diff --git a/modules/markup/markdown/goldmark.go b/modules/markup/markdown/goldmark.go
index b28fa9824e..35ecc77b5a 100644
--- a/modules/markup/markdown/goldmark.go
+++ b/modules/markup/markdown/goldmark.go
@@ -86,8 +86,10 @@ func (g *ASTTransformer) Transform(node *ast.Document, reader text.Reader, pc pa
 			tocNode := createTOCNode(tocList, rc.Lang, nil)
 			node.InsertBefore(node, firstChild, tocNode)
 		} else {
-			tocNode := createTOCNode(tocList, rc.Lang, map[string]string{"open": "open"})
-			ctx.SidebarTocNode = tocNode
+			ctx.SidebarTocHeaders = make([]markup.Header, len(tocList))
+			for i, h := range tocList {
+				ctx.SidebarTocHeaders[i] = markup.Header{Level: h.Level, Text: h.Text, ID: h.ID}
+			}
 		}
 	}
 
diff --git a/modules/markup/orgmode/orgmode.go b/modules/markup/orgmode/orgmode.go
index 93c335d244..c015d52636 100644
--- a/modules/markup/orgmode/orgmode.go
+++ b/modules/markup/orgmode/orgmode.go
@@ -96,7 +96,16 @@ func Render(ctx *markup.RenderContext, input io.Reader, output io.Writer) error
 	w := &orgWriter{rctx: ctx, HTMLWriter: htmlWriter}
 	htmlWriter.ExtendingWriter = w
 
-	res, err := org.New().Silent().Parse(input, "").Write(w)
+	// Parse the document first to extract outline for TOC
+	doc := org.New().Silent().Parse(input, "")
+	if doc.Error != nil {
+		return fmt.Errorf("orgmode.Parse failed: %w", doc.Error)
+	}
+
+	// Extract headers from the document outline for sidebar TOC
+	ctx.SidebarTocHeaders = extractHeadersFromOutline(doc.Outline)
+
+	res, err := doc.Write(w)
 	if err != nil {
 		return fmt.Errorf("orgmode.Render failed: %w", err)
 	}
@@ -104,6 +113,37 @@ func Render(ctx *markup.RenderContext, input io.Reader, output io.Writer) error
 	return err
 }
 
+// extractHeadersFromOutline recursively extracts headers from org document outline
+func extractHeadersFromOutline(outline org.Outline) []markup.Header {
+	var headers []markup.Header
+	collectHeaders(outline.Section, &headers)
+	return headers
+}
+
+// collectHeaders recursively collects headers from sections
+func collectHeaders(section *org.Section, headers *[]markup.Header) {
+	if section == nil {
+		return
+	}
+
+	// Process current section's headline
+	if section.Headline != nil {
+		h := section.Headline
+		// Convert headline title nodes to plain text
+		titleText := org.String(h.Title...)
+		*headers = append(*headers, markup.Header{
+			Level: h.Lvl,
+			Text:  titleText,
+			ID:    h.ID(),
+		})
+	}
+
+	// Process child sections
+	for _, child := range section.Children {
+		collectHeaders(child, headers)
+	}
+}
+
 // RenderString renders orgmode string to HTML string
 func RenderString(ctx *markup.RenderContext, content string) (string, error) {
 	var buf strings.Builder
diff --git a/modules/markup/render.go b/modules/markup/render.go
index 12f002b0c6..f09aea8e0b 100644
--- a/modules/markup/render.go
+++ b/modules/markup/render.go
@@ -18,7 +18,6 @@ import (
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/util"
 
-	"github.com/yuin/goldmark/ast"
 	"golang.org/x/sync/errgroup"
 )
 
@@ -36,6 +35,13 @@ var RenderBehaviorForTesting struct {
 	DisableAdditionalAttributes bool
 }
 
+// Header holds the data about a header for generating TOC
+type Header struct {
+	Level int
+	Text  string
+	ID    string
+}
+
 type RenderOptions struct {
 	UseAbsoluteLink bool
 
@@ -67,7 +73,7 @@ type RenderContext struct {
 	// the context might be used by the "render" function, but it might also be used by "postProcess" function
 	usedByRender bool
 
-	SidebarTocNode ast.Node
+	SidebarTocHeaders []Header // Headers for generating sidebar TOC
 
 	RenderHelper   RenderHelper
 	RenderOptions  RenderOptions
diff --git a/modules/markup/sidebar_toc.go b/modules/markup/sidebar_toc.go
new file mode 100644
index 0000000000..441e540d6a
--- /dev/null
+++ b/modules/markup/sidebar_toc.go
@@ -0,0 +1,77 @@
+// Copyright 2024 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package markup
+
+import (
+	"html"
+	"html/template"
+	"net/url"
+	"strings"
+
+	"code.gitea.io/gitea/modules/translation"
+)
+
+// RenderSidebarTocHTML renders a list of headers into HTML for sidebar TOC display.
+// It generates a <details> element with nested <ul> lists representing the header hierarchy.
+func RenderSidebarTocHTML(headers []Header, lang string) template.HTML {
+	if len(headers) == 0 {
+		return ""
+	}
+
+	var sb strings.Builder
+
+	// Start with <details open>
+	sb.WriteString(`<details open>`)
+	sb.WriteString(`<summary>`)
+	sb.WriteString(html.EscapeString(translation.NewLocale(lang).TrString("toc")))
+	sb.WriteString(`</summary>`)
+
+	// Find the minimum level to start with
+	minLevel := 6
+	for _, header := range headers {
+		if header.Level < minLevel {
+			minLevel = header.Level
+		}
+	}
+
+	// Build nested list structure
+	currentLevel := minLevel
+	sb.WriteString(`<ul>`)
+	openLists := 1
+
+	for _, header := range headers {
+		// Close lists if we need to go up levels
+		for currentLevel > header.Level {
+			sb.WriteString(`</ul>`)
+			openLists--
+			currentLevel--
+		}
+
+		// Open new lists if we need to go down levels
+		for currentLevel < header.Level {
+			sb.WriteString(`<ul>`)
+			openLists++
+			currentLevel++
+		}
+
+		// Write the list item with link
+		sb.WriteString(`<li>`)
+		sb.WriteString(`<a href="#`)
+		sb.WriteString(url.QueryEscape(header.ID))
+		sb.WriteString(`">`)
+		sb.WriteString(html.EscapeString(header.Text))
+		sb.WriteString(`</a>`)
+		sb.WriteString(`</li>`)
+	}
+
+	// Close all remaining open lists
+	for openLists > 0 {
+		sb.WriteString(`</ul>`)
+		openLists--
+	}
+
+	sb.WriteString(`</details>`)
+
+	return template.HTML(sb.String())
+}
diff --git a/routers/web/repo/view.go b/routers/web/repo/view.go
index 8e85cc3278..4bbad1a02e 100644
--- a/routers/web/repo/view.go
+++ b/routers/web/repo/view.go
@@ -179,6 +179,13 @@ func markupRender(ctx *context.Context, renderCtx *markup.RenderContext, input i
 	return escaped, output, err
 }
 
+func renderSidebarTocHTML(rctx *markup.RenderContext, lang string) template.HTML {
+	if len(rctx.SidebarTocHeaders) > 0 {
+		return markup.RenderSidebarTocHTML(rctx.SidebarTocHeaders, lang)
+	}
+	return ""
+}
+
 func checkHomeCodeViewable(ctx *context.Context) {
 	if ctx.Repo.HasUnits() {
 		if ctx.Repo.Repository.IsBeingCreated() {
diff --git a/routers/web/repo/view_file.go b/routers/web/repo/view_file.go
index 167cd5f927..4d96fb19c0 100644
--- a/routers/web/repo/view_file.go
+++ b/routers/web/repo/view_file.go
@@ -92,6 +92,8 @@ func handleFileViewRenderMarkup(ctx *context.Context, filename string, sniffedTy
 		ctx.ServerError("Render", err)
 		return true
 	}
+
+	ctx.Data["FileSidebarHTML"] = renderSidebarTocHTML(rctx, ctx.Locale.Language())
 	return true
 }
 
diff --git a/routers/web/repo/view_readme.go b/routers/web/repo/view_readme.go
index f1fa5732f0..ac44b7f59b 100644
--- a/routers/web/repo/view_readme.go
+++ b/routers/web/repo/view_readme.go
@@ -206,6 +206,8 @@ func prepareToRenderReadmeFile(ctx *context.Context, subfolder string, readmeFil
 			log.Error("Render failed for %s in %-v: %v Falling back to rendering source", readmeFile.Name(), ctx.Repo.Repository, err)
 			delete(ctx.Data, "IsMarkup")
 		}
+
+		ctx.Data["FileSidebarHTML"] = renderSidebarTocHTML(rctx, ctx.Locale.Language())
 	}
 
 	if ctx.Data["IsMarkup"] != true {
diff --git a/routers/web/repo/wiki.go b/routers/web/repo/wiki.go
index 921e17fb6a..165eb54d00 100644
--- a/routers/web/repo/wiki.go
+++ b/routers/web/repo/wiki.go
@@ -277,12 +277,9 @@ func renderViewPage(ctx *context.Context) (*git.Repository, *git.TreeEntry) {
 		return nil, nil
 	}
 
-	if rctx.SidebarTocNode != nil {
-		sb := strings.Builder{}
-		if err = markdown.SpecializedMarkdown(rctx).Renderer().Render(&sb, nil, rctx.SidebarTocNode); err != nil {
-			log.Error("Failed to render wiki sidebar TOC: %v", err)
-		}
-		ctx.Data["WikiSidebarTocHTML"] = templates.SanitizeHTML(sb.String())
+	// Render sidebar TOC
+	if len(rctx.SidebarTocHeaders) > 0 {
+		ctx.Data["WikiSidebarTocHTML"] = markup.RenderSidebarTocHTML(rctx.SidebarTocHeaders, ctx.Locale.Language())
 	}
 
 	if !isSideBar {
diff --git a/templates/repo/view_file.tmpl b/templates/repo/view_file.tmpl
index 809b1e9677..721c795617 100644
--- a/templates/repo/view_file.tmpl
+++ b/templates/repo/view_file.tmpl
@@ -35,6 +35,9 @@
 			{{end}}
 		</div>
 		<div class="file-header-right file-actions flex-text-block tw-flex-wrap">
+		{{if .FileSidebarHTML}}
+			<button class="btn-octicon" id="toggle-sidebar-btn" data-tooltip-content="{{ctx.Locale.Tr "toc"}}">{{svg "octicon-list-unordered" 15}}</button>
+		{{end}}
 			{{/* this componment is also controlled by frontend plugin renders */}}
 			<div class="ui compact icon buttons file-view-toggle-buttons {{Iif .HasSourceRenderedToggle "" "tw-hidden"}}">
 				{{if .IsRepresentableAsText}}
@@ -139,6 +142,11 @@
 				</div>
 			{{end}}
 		</div>
+		{{if .FileSidebarHTML}}
+		<div class="file-view-sidebar markup sidebar-panel-hidden">
+			{{.FileSidebarHTML}}
+		</div>
+		{{end}}
 
 		<div class="code-line-menu tippy-target">
 			{{if $.Permission.CanRead ctx.Consts.RepoUnitTypeIssues}}
diff --git a/web_src/css/repo.css b/web_src/css/repo.css
index abb891cf9b..6da0bf71cd 100644
--- a/web_src/css/repo.css
+++ b/web_src/css/repo.css
@@ -167,6 +167,9 @@ td .commit-summary {
   padding: 8px;
   vertical-align: middle;
   color: var(--color-text);
+  background: none;
+  border: none;
+  cursor: pointer;
 }
 
 .non-diff-file-content .header .file-actions .btn-octicon:hover {
diff --git a/web_src/css/repo/home.css b/web_src/css/repo/home.css
index 60bf1f17f9..3f3bbd1d6a 100644
--- a/web_src/css/repo/home.css
+++ b/web_src/css/repo/home.css
@@ -76,6 +76,12 @@
 .repo-view-content {
   flex: 1;
   min-width: 0;
+  transition: margin-right 0.2s ease;
+}
+
+/* When sidebar is visible, reserve space on the right (only for file view, not home page) */
+.repo-view-content.sidebar-visible {
+  margin-right: 270px;
 }
 
 .language-stats {
@@ -105,3 +111,100 @@
   padding: 0 0.5em; /* make the UI look better for narrow (mobile) view */
   text-decoration: none;
 }
+
+/* File view sidebar panel (e.g., TOC for markdown files) */
+.file-view-sidebar {
+  position: fixed;
+  top: 120px; /* Will be adjusted by JS to align with file content */
+  right: 0.5rem;
+  width: 260px;
+  max-height: calc(100vh - 140px);
+  overflow-y: auto;
+  padding: 0.75rem;
+  background: var(--color-box-body);
+  border: 1px solid var(--color-secondary);
+  border-radius: var(--border-radius);
+  z-index: 50;
+  opacity: 0; /* Hidden until JS positions it */
+  transition: opacity 0.15s ease;
+}
+
+/* Show sidebar after JS has positioned it */
+.file-view-sidebar.sidebar-positioned {
+  opacity: 1;
+}
+
+/* Hidden state - using custom class to avoid Tailwind conflicts */
+.file-view-sidebar.sidebar-panel-hidden {
+  display: none;
+}
+
+.file-view-sidebar details {
+  font-size: 13px;
+}
+
+.file-view-sidebar summary {
+  font-weight: var(--font-weight-semibold);
+  cursor: pointer;
+  padding: 8px 0;
+  color: var(--color-text);
+  border-bottom: 1px solid var(--color-secondary);
+  margin-bottom: 8px;
+}
+
+.file-view-sidebar ul {
+  margin: 0;
+  list-style: none;
+  padding: 5px 0 5px 1em;
+}
+
+.file-view-sidebar ul ul {
+  border-left: 1px dashed var(--color-secondary);
+}
+
+.file-view-sidebar a {
+  display: block;
+  padding: 6px 10px;
+  color: var(--color-text);
+  text-decoration: none;
+  font-size: 13px;
+  line-height: 1.4;
+  border-radius: var(--border-radius);
+}
+
+.file-view-sidebar a:hover {
+  color: var(--color-primary);
+  background: var(--color-hover);
+}
+
+/* Sidebar toggle button styling for file view (not readme) - add border to match other buttons */
+.file-header-right #toggle-sidebar-btn {
+  border: 1px solid var(--color-secondary);
+  border-radius: var(--border-radius);
+}
+
+.file-header-right #toggle-sidebar-btn:hover {
+  border-color: var(--color-primary);
+}
+
+/* Sidebar toggle button active state - when sidebar is visible */
+#toggle-sidebar-btn.active {
+  color: var(--color-primary);
+  border-color: var(--color-primary);
+}
+
+/* Hide sidebar on small screens (phones) */
+@media (max-width: 768px) {
+  .file-view-sidebar {
+    display: none !important;
+  }
+
+  #toggle-sidebar-btn {
+    display: none;
+  }
+
+  /* Don't reserve space for sidebar on small screens */
+  .repo-view-content.sidebar-visible {
+    margin-right: 0;
+  }
+}
diff --git a/web_src/js/features/file-view.ts b/web_src/js/features/file-view.ts
index ff9e8cfa26..de1d00e49c 100644
--- a/web_src/js/features/file-view.ts
+++ b/web_src/js/features/file-view.ts
@@ -59,9 +59,145 @@ async function renderRawFileToContainer(container: HTMLElement, rawFileLink: str
   }
 }
 
+function updateSidebarPosition(elFileView: HTMLElement, sidebar: HTMLElement): void {
+  const fileHeader = elFileView.querySelector('.file-header');
+  const segment = elFileView.querySelector('.ui.bottom.segment');
+  if (!fileHeader || !segment) return;
+
+  const headerRect = fileHeader.getBoundingClientRect();
+  const segmentRect = segment.getBoundingClientRect();
+
+  // Calculate top position:
+  // - When file header is visible: align with file header top
+  // - When file header scrolls above viewport: stick to top (12px)
+  // - Ensure sidebar top doesn't go above segment top (when scrolling up)
+  const minTop = 12;
+  let topPos = Math.max(minTop, headerRect.top);
+  topPos = Math.max(topPos, segmentRect.top); // Don't go above segment top
+
+  // Dynamically calculate max-height so sidebar doesn't extend below segment bottom
+  const availableHeight = Math.max(0, segmentRect.bottom - topPos);
+  const cssMaxHeight = window.innerHeight - 140; // Match CSS calc(100vh - 140px)
+  const maxHeight = Math.min(availableHeight, cssMaxHeight);
+
+  // Hide sidebar if available height is too small
+  if (maxHeight < 50) {
+    sidebar.style.opacity = '0';
+    return;
+  }
+
+  sidebar.style.maxHeight = `${maxHeight}px`;
+  sidebar.style.opacity = '';
+  sidebar.style.top = `${topPos}px`;
+
+  // Position sidebar right next to the content
+  const leftPos = segmentRect.right + 8; // 8px gap from content
+  sidebar.style.left = `${leftPos}px`;
+  sidebar.style.right = 'auto';
+
+  // Mark as positioned to show the sidebar (prevents flicker)
+  sidebar.classList.add('sidebar-positioned');
+}
+
+function initSidebarToggle(elFileView: HTMLElement): void {
+  const toggleBtn = elFileView.querySelector('#toggle-sidebar-btn');
+  const sidebar = elFileView.querySelector<HTMLElement>('.file-view-sidebar');
+  if (!toggleBtn || !sidebar) return;
+
+  // Check if we're in file view (not home page) - only file view needs margin adjustment
+  const repoViewContent = elFileView.closest('.repo-view-content');
+  const isFileView = Boolean(repoViewContent);
+
+  // Helper to update position
+  const updatePosition = () => {
+    if (!sidebar.classList.contains('sidebar-panel-hidden')) {
+      updateSidebarPosition(elFileView, sidebar);
+    }
+  };
+
+  // Helper to show sidebar with proper positioning
+  const showSidebar = () => {
+    toggleBtn.classList.add('active');
+
+    // Wait for margin to take effect before showing and positioning sidebar
+    const showAfterLayout = () => {
+      sidebar.classList.remove('sidebar-panel-hidden');
+      requestAnimationFrame(() => {
+        updateSidebarPosition(elFileView, sidebar);
+      });
+    };
+
+    // For file view, first add margin, wait for layout, then show sidebar
+    if (isFileView && repoViewContent) {
+      repoViewContent.classList.add('sidebar-visible');
+      // Wait for CSS transition to complete (200ms) before calculating position
+      setTimeout(showAfterLayout, 220);
+    } else {
+      // For home page (README), no margin needed, show with small delay
+      setTimeout(showAfterLayout, 10);
+    }
+  };
+
+  // Helper to hide sidebar
+  const hideSidebar = () => {
+    sidebar.classList.add('sidebar-panel-hidden');
+    sidebar.classList.remove('sidebar-positioned');
+    toggleBtn.classList.remove('active');
+    if (isFileView && repoViewContent) {
+      repoViewContent.classList.remove('sidebar-visible');
+    }
+  };
+
+  // Restore saved state from localStorage (default to hidden)
+  const savedState = localStorage.getItem('file-view-sidebar-visible');
+  const isVisible = savedState === 'true'; // default to hidden
+
+  // Apply initial state
+  if (isVisible) {
+    showSidebar();
+  } else {
+    hideSidebar();
+  }
+
+  // Update sidebar position on resize/scroll to keep aligned with file content
+  const resizeObserver = new ResizeObserver(() => {
+    updatePosition();
+  });
+  resizeObserver.observe(document.body);
+
+  // Update position using IntersectionObserver instead of scroll event
+  // This provides better performance and avoids scroll event issues
+  const fileHeader = elFileView.querySelector('.file-header');
+  const segment = elFileView.querySelector('.ui.bottom.segment');
+  if (fileHeader && segment) {
+    // Use many thresholds to get fine-grained position updates during scroll
+    const thresholds = Array.from({length: 101}, (_, i) => i / 100);
+    const positionObserver = new IntersectionObserver(() => {
+      updatePosition();
+    }, {threshold: thresholds});
+    positionObserver.observe(segment);
+    positionObserver.observe(fileHeader);
+  }
+
+  toggleBtn.addEventListener('click', () => {
+    const isCurrentlyVisible = !sidebar.classList.contains('sidebar-panel-hidden');
+    if (isCurrentlyVisible) {
+      hideSidebar();
+      localStorage.setItem('file-view-sidebar-visible', 'false');
+    } else {
+      showSidebar();
+      localStorage.setItem('file-view-sidebar-visible', 'true');
+    }
+  });
+}
+
 export function initRepoFileView(): void {
   registerGlobalInitFunc('initRepoFileView', async (elFileView: HTMLElement) => {
     initPluginsOnce();
+
+    // Initialize sidebar toggle functionality (e.g., TOC for markdown files)
+    initSidebarToggle(elFileView);
+
     const rawFileLink = elFileView.getAttribute('data-raw-file-link')!;
     const mimeType = elFileView.getAttribute('data-mime-type') || ''; // not used yet
     // TODO: we should also provide the prefetched file head bytes to let the plugin decide whether to render or not