diff --git a/README.md b/README.md
index 401a230..27e1660 100644
--- a/README.md
+++ b/README.md
@@ -138,6 +138,31 @@ Described at [documentation](https://github.com/stradichenko/PKB-theme/blob/main
 
 ### [Color Theme Customization](https://stradichenko.github.io/PKB-theme/docs/color-theme-customization)
 
+### Internationalization (i18n)
+
+The theme uses Hugo's built-in [i18n](https://gohugo.io/content-management/multilingual/) system so that template strings can be translated. All user-facing strings live in `i18n/en.toml` at the theme root, and templates reference them via `{{ T "key" }}`.
+
+To add a translation:
+
+1. Copy `i18n/en.toml` to `i18n/<lang>.toml` (e.g. `i18n/es.toml` for Spanish) and translate the values, leaving the keys unchanged.
+2. Register the new language in `config/_default/hugo.toml` under the `[languages]` block:
+
+   ```toml
+   [languages]
+     [languages.en]
+       languageName = "English"
+       languageCode = "en-US"
+       weight = 1
+     [languages.es]
+       languageName = "Español"
+       languageCode = "es-ES"
+       weight = 2
+   ```
+
+3. Optionally, override individual strings from your own site by creating an `i18n/<lang>.toml` file in your project root — Hugo's lookup order will prefer your project's translations over the theme's defaults.
+
+See [Hugo's multilingual documentation](https://gohugo.io/content-management/multilingual/) for full details on translating content, menus, and dates.
+
 
 ## FAQ
 ### Hugo's Theme Configuration Inheritance (Lookup Order)
diff --git a/config/_default/hugo.toml b/config/_default/hugo.toml
index a01c33d..88bd991 100644
--- a/config/_default/hugo.toml
+++ b/config/_default/hugo.toml
@@ -2,6 +2,9 @@ baseURL = 'https://example.org/'
 languageCode = 'en-us'
 title = 'HUGO_site'
 
+defaultContentLanguage = "en"
+defaultContentLanguageInSubdir = false
+
 enableGitInfo = true
 #relativeURLs = true
 #canonifyURLs = true
@@ -518,4 +521,10 @@ enableGitInfo = true
   filename = 'sitemap.xml'
   priority = -1
 
-uglyURLs = false
\ No newline at end of file
+uglyURLs = false
+
+[languages]
+  [languages.en]
+    languageName = "English"
+    languageCode = "en-US"
+    weight = 1
\ No newline at end of file
diff --git a/i18n/en.toml b/i18n/en.toml
new file mode 100644
index 0000000..e1a64b4
--- /dev/null
+++ b/i18n/en.toml
@@ -0,0 +1,103 @@
+# Common
+SiteTitle = "PKB Theme"
+ReadMore = "Read more"
+BackToTop = "Back to top"
+
+# Single post
+Created = "Created"
+Updated = "Updated"
+TableOfContents = "Table of Contents"
+Author = "Author"
+Tags = "Tags"
+Categories = "Categories"
+References = "References"
+Footnotes = "Footnotes"
+Citations = "Citations"
+
+# Search
+Search = "Search"
+SearchPlaceholder = "Search…"
+SearchNoResults = "No results"
+SearchResultsFor = "Results for"
+
+# Theme toggle
+ToggleTheme = "Toggle theme"
+ThemeLight = "Light"
+ThemeDark = "Dark"
+
+# Share
+Share = "Share"
+ShareModalTitle = "Share this page"
+CopyLink = "Copy link"
+LinkCopied = "Link copied!"
+
+# QR
+QRCode = "QR code"
+QRCodeFor = "QR code for"
+
+# About page
+NoSocialLinks = "No social links available."
+NoInterests = "No interests listed."
+Interests = "Interests"
+
+# PDF
+GeneratePDF = "Generate PDF"
+PrintToPDF = "Print to PDF"
+
+# TTS
+ListenToPage = "Listen to this page"
+TTSSystemVoice = "System Voice"
+TTSBrowserBuiltin = "Browser built-in"
+TTSNeuralHD = "Neural HD"
+TTSOnetimeDownload = "One-time download · cached locally"
+TTSPlay = "Play"
+TTSPause = "Pause"
+TTSStop = "Stop"
+
+# Knowledge graph
+KGPhysicsControls = "Physics Controls"
+KGRepulsion = "Repulsion"
+KGResetToDefault = "Reset to Default"
+KGAllNodes = "All Nodes"
+KGSaveAsPNG = "Save as PNG"
+KGSaveAsSVG = "Save as SVG"
+KGSaveAsJPEG = "Save as JPEG"
+KGFullscreen = "Fullscreen"
+
+# Activity calendar
+ActivityCalendar = "Activity Calendar"
+CalendarLess = "Less"
+CalendarMore = "More"
+CalendarContributions = "contributions"
+CalendarNoActivity = "No activity"
+
+# Zipf's law / LDA
+ZipfTitle = "Zipf's Law"
+ZipfWord = "Word"
+ZipfFrequency = "Frequency"
+ZipfRank = "Rank"
+LDATopics = "Topics"
+LDADocument = "Document"
+LDATopicNumber = "Topic"
+
+# Filters
+FilterByTag = "Filter by tag"
+FilterByCategory = "Filter by category"
+FilterClear = "Clear filters"
+FilterAll = "All"
+
+# 404 page
+NotFoundTitle = "404 — Page Not Found"
+NotFoundMessage = "The page you are looking for could not be found."
+NotFoundReturnHome = "Return home"
+
+# Comments
+CommentsLoading = "Loading comments…"
+CommentsDisabled = "Comments are disabled."
+
+# Misc
+PoweredBy = "Powered by"
+GeneratedBy = "Generated by"
+LoadingMore = "Loading more…"
+Error = "Error"
+AnchorLabel = "Permalink to this section"