diff --git a/i18n-helpers/src/gettext.rs b/i18n-helpers/src/gettext.rs
index 7733b312..3794fd5c 100644
--- a/i18n-helpers/src/gettext.rs
+++ b/i18n-helpers/src/gettext.rs
@@ -40,7 +40,7 @@ fn strip_formatting(text: &str) -> String {
         .collect()
 }
 
-fn translate(text: &str, catalog: &Catalog) -> anyhow::Result<String> {
+pub(crate) fn translate(text: &str, catalog: &Catalog) -> anyhow::Result<String> {
     let events = extract_events(text, None);
     // Translation should always succeed.
     let translated_events = translate_events(&events, catalog).expect("Failed to translate events");
diff --git a/i18n-helpers/src/preprocessors/gettext.rs b/i18n-helpers/src/preprocessors/gettext.rs
index 42d5fd02..ff82f158 100644
--- a/i18n-helpers/src/preprocessors/gettext.rs
+++ b/i18n-helpers/src/preprocessors/gettext.rs
@@ -12,13 +12,183 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use crate::gettext::{add_stripped_summary_translations, translate_book};
+use crate::gettext::{add_stripped_summary_translations, translate, translate_book};
 use anyhow::{anyhow, Context};
+use mdbook::book::{Book, BookItem};
 use mdbook::preprocess::{Preprocessor, PreprocessorContext};
 use polib::catalog::Catalog;
 use polib::po_file;
 use std::path::PathBuf;
 
+#[derive(Debug, Default, PartialEq, Eq)]
+struct MetadataTranslations {
+    title: Option<String>,
+    description: Option<String>,
+}
+
+fn metadata_translations(
+    title: Option<&str>,
+    description: Option<&str>,
+    catalog: &Catalog,
+) -> anyhow::Result<MetadataTranslations> {
+    let mut translations = MetadataTranslations::default();
+
+    if let Some(title) = title {
+        let translated = translate(title, catalog)?;
+        if translated.trim() != title.trim() {
+            translations.title = Some(translated);
+        }
+    }
+
+    if let Some(description) = description {
+        let translated = translate(description, catalog)?;
+        if translated.trim() != description.trim() {
+            translations.description = Some(translated);
+        }
+    }
+
+    Ok(translations)
+}
+
+fn metadata_script(translations: &MetadataTranslations) -> Option<String> {
+    if translations.title.is_none() && translations.description.is_none() {
+        return None;
+    }
+
+    // Serialize eagerly so we fail early if escaping fails for some reason.
+    let title_json = translations
+        .title
+        .as_ref()
+        .map(|t| serde_json::to_string(t))
+        .transpose()
+        .ok()?;
+    let description_json = translations
+        .description
+        .as_ref()
+        .map(|d| serde_json::to_string(d))
+        .transpose()
+        .ok()?;
+
+    let mut script =
+        String::from("\n\n<script>window.addEventListener('DOMContentLoaded', function () {\n");
+    if let Some(title) = title_json {
+        script.push_str("  const title = ");
+        script.push_str(&title);
+        script.push_str(
+            ";\n  if (title) {\n    document.title = title;\n    for (const el of document.querySelectorAll('.menu-title, .mobile-nav__title')) {\n      el.textContent = title;\n    }\n  }\n",
+        );
+    }
+
+    if let Some(description) = description_json {
+        script.push_str("  const description = ");
+        script.push_str(&description);
+        script.push_str(
+            ";\n  if (description) {\n    const meta = document.querySelector('meta[name=\"description\"]');\n    if (meta) {\n      meta.setAttribute('content', description);\n    }\n  }\n",
+        );
+    }
+
+    script.push_str("});</script>\n");
+    Some(script)
+}
+
+fn inject_metadata_script(book: &mut Book, translations: &MetadataTranslations) {
+    if let Some(script) = metadata_script(translations) {
+        book.for_each_mut(|item| {
+            if let BookItem::Chapter(ch) = item {
+                ch.content.push_str(&script);
+            }
+        });
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use mdbook::book::{Book, BookItem, Chapter};
+    use polib::message::Message;
+    use polib::metadata::CatalogMetadata;
+
+    fn catalog_with(entries: &[(&str, &str)]) -> Catalog {
+        let mut catalog = Catalog::new(CatalogMetadata::new());
+        for (msgid, msgstr) in entries {
+            let message = Message::build_singular()
+                .with_msgid((*msgid).to_string())
+                .with_msgstr((*msgstr).to_string())
+                .done();
+            catalog.append_or_update(message);
+        }
+        catalog
+    }
+
+    #[test]
+    fn injects_script_when_metadata_translated() {
+        let catalog = catalog_with(&[
+            ("Original Title", "Titre traduit"),
+            ("Original description", "Description traduite"),
+        ]);
+
+        let translations = metadata_translations(
+            Some("Original Title"),
+            Some("Original description"),
+            &catalog,
+        )
+        .unwrap();
+        assert_eq!(
+            translations,
+            MetadataTranslations {
+                title: Some("Titre traduit".into()),
+                description: Some("Description traduite".into()),
+            }
+        );
+
+        let mut book = Book::new();
+        book.push_item(BookItem::Chapter(Chapter::new(
+            "Chapter",
+            "# Heading".into(),
+            "chapter.md",
+            vec![],
+        )));
+
+        inject_metadata_script(&mut book, &translations);
+
+        let mut contents = Vec::new();
+        book.for_each_mut(|item| {
+            if let BookItem::Chapter(ch) = item {
+                contents.push(ch.content.clone());
+            }
+        });
+
+        assert!(contents[0].contains("Titre traduit"));
+        assert!(contents[0].contains("Description traduite"));
+        assert!(contents[0].contains("window.addEventListener"));
+    }
+
+    #[test]
+    fn skips_script_when_no_translation() {
+        let catalog = catalog_with(&[("Same Title", "Same Title"), ("Same description", "")]);
+
+        let translations =
+            metadata_translations(Some("Same Title"), Some("Same description"), &catalog).unwrap();
+        assert_eq!(translations, MetadataTranslations::default());
+
+        let mut book = Book::new();
+        book.push_item(BookItem::Chapter(Chapter::new(
+            "Chapter",
+            "Content".into(),
+            "chapter.md",
+            vec![],
+        )));
+
+        inject_metadata_script(&mut book, &translations);
+
+        book.for_each_mut(|item| {
+            if let BookItem::Chapter(ch) = item {
+                assert!(!ch.content.contains("</script>"));
+            }
+        });
+    }
+}
+
 /// Check whether the book should be transalted.
 ///
 /// The book should be translated if:
@@ -80,7 +250,13 @@ impl Preprocessor for Gettext {
         if should_translate(ctx) {
             let mut catalog = load_catalog(ctx)?;
             add_stripped_summary_translations(&mut catalog);
+            let metadata = metadata_translations(
+                ctx.config.book.title.as_deref(),
+                ctx.config.book.description.as_deref(),
+                &catalog,
+            )?;
             translate_book(&catalog, &mut book)?;
+            inject_metadata_script(&mut book, &metadata);
         }
         Ok(book)
     }
diff --git a/i18n-helpers/src/xgettext.rs b/i18n-helpers/src/xgettext.rs
index 4b66798f..d9574bb2 100644
--- a/i18n-helpers/src/xgettext.rs
+++ b/i18n-helpers/src/xgettext.rs
@@ -140,7 +140,31 @@ where
             })?,
     };
 
-    // First, add all chapter names and part titles from SUMMARY.md.
+    // Include book level metadata from book.toml so translators can localize
+    // what readers see in the book chrome.
+    let book_toml_path = Path::new("book.toml");
+    if let Some(title) = ctx
+        .config
+        .book
+        .title
+        .as_ref()
+        .filter(|t| !t.trim().is_empty())
+    {
+        let source = build_source(book_toml_path, 1, granularity);
+        add_message(&mut catalog, title, &source, "");
+    }
+    if let Some(description) = ctx
+        .config
+        .book
+        .description
+        .as_ref()
+        .filter(|d| !d.trim().is_empty())
+    {
+        let source = build_source(book_toml_path, 1, granularity);
+        add_message(&mut catalog, description, &source, "");
+    }
+
+    // Next, add all chapter names and part titles from SUMMARY.md.
     let summary_path = ctx.config.book.src.join("SUMMARY.md");
     let summary = summary_reader(ctx.root.join(&summary_path))
         .with_context(|| anyhow!("Failed to read {}", summary_path.display()))?;
@@ -382,6 +406,7 @@ mod tests {
                 "book.toml",
                 "[book]\n\
                  title = \"My Translatable Book\"\n\
+                 description = \"A lovely book\"\n\
                  language = \"fr\"",
             ),
             ("src/SUMMARY.md", ""),
@@ -393,6 +418,16 @@ mod tests {
         let catalog = &catalogs[&default_template_file()];
         assert_eq!(catalog.metadata.project_id_version, "My Translatable Book");
         assert_eq!(catalog.metadata.language, "fr");
+        assert_eq!(
+            catalog
+                .messages()
+                .map(|msg| (msg.source(), msg.msgid(), msg.comments()))
+                .collect::<Vec<_>>(),
+            vec![
+                ("book.toml:1", "My Translatable Book", ""),
+                ("book.toml:1", "A lovely book", ""),
+            ]
+        );
         Ok(())
     }