diff --git a/browser/components/customizableui/CustomizableWidgets.jsm b/browser/components/customizableui/CustomizableWidgets.jsm
index a78ea7f74f37..6cc5d8a018a0 100644
--- a/browser/components/customizableui/CustomizableWidgets.jsm
+++ b/browser/components/customizableui/CustomizableWidgets.jsm
@@ -793,11 +793,54 @@ if (Services.prefs.getBoolPref("privacy.panicButton.enabled")) {
       }
     },
     onViewShowing(aEvent) {
+      let win = aEvent.target.ownerGlobal;
+      let doc = win.document;
+      let eventBlocker = null;
+      if (!doc.querySelector("#PanelUI-panic-timeframe")) {
+        win.MozXULElement.insertFTLIfNeeded("browser/panicButton.ftl");
+        let frag = win.MozXULElement.parseXULToFragment(`
+          <vbox class="panel-subview-body">
+            <hbox id="PanelUI-panic-timeframe">
+              <image id="PanelUI-panic-timeframe-icon" alt=""/>
+              <vbox flex="1">
+                <description data-l10n-id="panic-main-timeframe-desc" id="PanelUI-panic-mainDesc"></description>
+                <radiogroup id="PanelUI-panic-timeSpan" aria-labelledby="PanelUI-panic-mainDesc" closemenu="none">
+                  <radio id="PanelUI-panic-5min" data-l10n-id="panic-button-5min" selected="true"
+                        value="5" class="subviewradio"/>
+                  <radio id="PanelUI-panic-2hr" data-l10n-id="panic-button-2hr"
+                        value="2" class="subviewradio"/>
+                  <radio id="PanelUI-panic-day" data-l10n-id="panic-button-day"
+                        value="6" class="subviewradio"/>
+                </radiogroup>
+              </vbox>
+            </hbox>
+            <vbox id="PanelUI-panic-explanations">
+              <label id="PanelUI-panic-actionlist-main-label" data-l10n-id="panic-button-action-desc"></label>
+
+              <label id="PanelUI-panic-actionlist-windows" class="PanelUI-panic-actionlist" data-l10n-id="panic-button-delete-tabs-and-windows"></label>
+              <label id="PanelUI-panic-actionlist-cookies" class="PanelUI-panic-actionlist" data-l10n-id="panic-button-delete-cookies"></label>
+              <label id="PanelUI-panic-actionlist-history" class="PanelUI-panic-actionlist" data-l10n-id="panic-button-delete-history"></label>
+              <label id="PanelUI-panic-actionlist-newwindow" class="PanelUI-panic-actionlist" data-l10n-id="panic-button-open-new-window"></label>
+
+              <label id="PanelUI-panic-warning" data-l10n-id="panic-button-undo-warning"></label>
+            </vbox>
+            <button id="PanelUI-panic-view-button"
+                    data-l10n-id="panic-button-forget-button"/>
+          </vbox>
+        `);
+
+        aEvent.target.appendChild(frag);
+        eventBlocker = doc.l10n.translateElements([aEvent.target]);
+      }
+
       let forgetButton = aEvent.target.querySelector("#PanelUI-panic-view-button");
-      let doc = aEvent.target.ownerDocument;
       let group = doc.getElementById("PanelUI-panic-timeSpan");
       group.selectedItem = doc.getElementById("PanelUI-panic-5min");
       forgetButton.addEventListener("command", this);
+
+      if (eventBlocker) {
+        aEvent.detail.addBlocker(eventBlocker);
+      }
     },
     onViewHiding(aEvent) {
       let forgetButton = aEvent.target.querySelector("#PanelUI-panic-view-button");
diff --git a/browser/components/customizableui/content/panelUI.inc.xul b/browser/components/customizableui/content/panelUI.inc.xul
index 63d32886c183..8815adce885b 100644
--- a/browser/components/customizableui/content/panelUI.inc.xul
+++ b/browser/components/customizableui/content/panelUI.inc.xul
@@ -633,34 +633,7 @@
 
     <panelview id="PanelUI-panicView" flex="1"
                descriptionheightworkaround="true">
-      <vbox class="panel-subview-body">
-        <hbox id="PanelUI-panic-timeframe">
-          <image id="PanelUI-panic-timeframe-icon" alt=""/>
-          <vbox flex="1">
-            <description id="PanelUI-panic-mainDesc">&panicButton.view.mainTimeframeDesc;</description>
-            <radiogroup id="PanelUI-panic-timeSpan" aria-labelledby="PanelUI-panic-mainDesc" closemenu="none">
-              <radio id="PanelUI-panic-5min" label="&panicButton.view.5min;" selected="true"
-                     value="5" class="subviewradio"/>
-              <radio id="PanelUI-panic-2hr" label="&panicButton.view.2hr;"
-                     value="2" class="subviewradio"/>
-              <radio id="PanelUI-panic-day" label="&panicButton.view.day;"
-                     value="6" class="subviewradio"/>
-            </radiogroup>
-          </vbox>
-        </hbox>
-        <vbox id="PanelUI-panic-explanations">
-          <label id="PanelUI-panic-actionlist-main-label">&panicButton.view.mainActionDesc;</label>
-
-          <label id="PanelUI-panic-actionlist-windows" class="PanelUI-panic-actionlist">&panicButton.view.deleteTabsAndWindows;</label>
-          <label id="PanelUI-panic-actionlist-cookies" class="PanelUI-panic-actionlist">&panicButton.view.deleteCookies;</label>
-          <label id="PanelUI-panic-actionlist-history" class="PanelUI-panic-actionlist">&panicButton.view.deleteHistory;</label>
-          <label id="PanelUI-panic-actionlist-newwindow" class="PanelUI-panic-actionlist">&panicButton.view.openNewWindow;</label>
-
-          <label id="PanelUI-panic-warning">&panicButton.view.undoWarning;</label>
-        </vbox>
-        <button id="PanelUI-panic-view-button"
-                label="&panicButton.view.forgetButton;"/>
-      </vbox>
+      <!-- This is constructed in CustomizableWidgets.jsm -->
     </panelview>
 
     <panelview id="appMenu-moreView" title="&moreMenu.label;" class="PanelUI-subView">
diff --git a/browser/locales/en-US/browser/panicButton.ftl b/browser/locales/en-US/browser/panicButton.ftl
new file mode 100644
index 000000000000..e4b0f2ef2066
--- /dev/null
+++ b/browser/locales/en-US/browser/panicButton.ftl
@@ -0,0 +1,31 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+panic-button-open-new-window = Open a new clean Window
+panic-button-undo-warning = This action cannot be undone.
+panic-button-forget-button =
+    .label = Forget!
+
+## These strings are combined to form a complete sentence starting with
+## panic-main-timeframe-desc. For example: "Forget the last: Five minutes".
+## Please ensure that this remains the case in the translation.
+
+panic-main-timeframe-desc = Forget the last:
+panic-button-5min =
+    .label = Five minutes
+panic-button-2hr =
+    .label = Two hours
+panic-button-day =
+    .label = 24 hours
+
+## These strings are combined to form a complete sentence starting with
+## panic-button-action-desc. For example: "Proceeding will: Delete Recent Cookies".
+## Please ensure that this remains the case in the translation.
+## Note also that some strings include <strong> tags for emphasis on the
+## words "Cookies", "History", "Tabs" and "Windows". The translation should do the same.
+
+panic-button-action-desc = Proceeding will:
+panic-button-delete-cookies = Delete Recent <strong>Cookies</strong>
+panic-button-delete-history = Delete Recent <strong>History</strong>
+panic-button-delete-tabs-and-windows = Close all <strong>Tabs</strong> and <strong>Windows</strong>
diff --git a/browser/locales/en-US/chrome/browser/browser.dtd b/browser/locales/en-US/chrome/browser/browser.dtd
index 48380740d8cd..62bca51794d0 100644
--- a/browser/locales/en-US/chrome/browser/browser.dtd
+++ b/browser/locales/en-US/chrome/browser/browser.dtd
@@ -968,27 +968,6 @@ you can use these alternative items. Otherwise, their values should be empty.  -
 
 <!ENTITY uiTour.infoPanel.close "Close">
 
-<!-- LOCALIZATION NOTE: (panicButton.view.mainTimeframeDesc, panicButton.view.5min, panicButton.view.2hr, panicButton.view.day):
-     The .mainTimeframeDesc string combined with any of the 3 others is meant to form a complete sentence, e.g. "Forget the last: Five minutes".
-     Please ensure that this remains the case in the translation. -->
-<!ENTITY panicButton.view.mainTimeframeDesc       "Forget the last:">
-<!ENTITY panicButton.view.5min                    "Five minutes">
-<!ENTITY panicButton.view.2hr                     "Two hours">
-<!ENTITY panicButton.view.day                     "24 hours">
-
-<!-- LOCALIZATION NOTE: (panicButton.view.mainLabel, panicButton.view.deleteCookies, panicButton.view.deleteHistory, panicButton.view.deleteTabsAndWindows, panicButton.view.openNewWindow):
-     The .mainActionDesc string combined with any of the 4 others is meant to form a complete sentence, e.g. "Proceeding will: Delete Recent Cookies".
-     Note also that the deleteCookies, deleteHistory and deleteTabsAndWindows strings include <html:strong> tags for emphasis on the words "Cookies", "History", "Tabs" and "Windows".
-     The translation should do the same. -->
-<!ENTITY panicButton.view.mainActionDesc          "Proceeding will:">
-<!ENTITY panicButton.view.deleteCookies           "Delete Recent <html:strong>Cookies</html:strong>">
-<!ENTITY panicButton.view.deleteHistory           "Delete Recent <html:strong>History</html:strong>">
-<!ENTITY panicButton.view.deleteTabsAndWindows    "Close all <html:strong>Tabs</html:strong> and <html:strong>Windows</html:strong>">
-<!ENTITY panicButton.view.openNewWindow           "Open a new clean Window">
-
-<!ENTITY panicButton.view.undoWarning             "This action cannot be undone.">
-<!ENTITY panicButton.view.forgetButton            "Forget!">
-
 <!ENTITY panicButton.thankyou.msg1                "Your recent history is cleared.">
 <!ENTITY panicButton.thankyou.msg2                "Safe browsing!">
 <!ENTITY panicButton.thankyou.buttonlabel         "Thanks!">
diff --git a/python/l10n/fluent_migrations/bug_1495861_panicButton.py b/python/l10n/fluent_migrations/bug_1495861_panicButton.py
new file mode 100644
index 000000000000..dc706f536c06
--- /dev/null
+++ b/python/l10n/fluent_migrations/bug_1495861_panicButton.py
@@ -0,0 +1,67 @@
+# coding=utf8
+
+# Any copyright is dedicated to the Public Domain.
+# http://creativecommons.org/publicdomain/zero/1.0/
+
+from __future__ import absolute_import
+import fluent.syntax.ast as FTL
+from fluent.migrate.helpers import transforms_from
+from fluent.migrate import COPY, REPLACE
+
+def migrate(ctx):
+    """Bug 1517508 - Migrate panicButton to use Fluent for localization, part {index}."""
+
+    ctx.add_transforms(
+        "browser/browser/panicButton.ftl",
+        "browser/browser/panicButton.ftl",
+        transforms_from(
+"""
+panic-button-open-new-window = { COPY("browser/chrome/browser/browser.dtd", "panicButton.view.openNewWindow") }
+panic-button-undo-warning = { COPY("browser/chrome/browser/browser.dtd", "panicButton.view.undoWarning") }
+panic-button-forget-button =
+    .label = { COPY("browser/chrome/browser/browser.dtd", "panicButton.view.forgetButton") }
+panic-main-timeframe-desc = { COPY("browser/chrome/browser/browser.dtd", "panicButton.view.mainTimeframeDesc") }
+panic-button-5min =
+    .label = { COPY("browser/chrome/browser/browser.dtd", "panicButton.view.5min") }
+panic-button-2hr =
+    .label = { COPY("browser/chrome/browser/browser.dtd", "panicButton.view.2hr") }
+panic-button-day =
+    .label = { COPY("browser/chrome/browser/browser.dtd", "panicButton.view.day") }
+panic-button-action-desc = { COPY("browser/chrome/browser/browser.dtd", "panicButton.view.mainActionDesc") }
+""")
+)
+
+    ctx.add_transforms(
+        "browser/browser/panicButton.ftl",
+        "browser/browser/panicButton.ftl", [
+		FTL.Message(
+			id=FTL.Identifier("panic-button-delete-cookies"),
+			value=REPLACE(
+				"browser/chrome/browser/browser.dtd",
+				"panicButton.view.deleteCookies",
+				{
+					"html:strong>": FTL.TextElement('strong>')
+				}
+			)
+		),
+		FTL.Message(
+			id=FTL.Identifier("panic-button-delete-history"),
+			value=REPLACE(
+				"browser/chrome/browser/browser.dtd",
+				"panicButton.view.deleteHistory",
+				{
+					"html:strong>": FTL.TextElement('strong>')
+				}
+			)
+		),
+		FTL.Message(
+			id=FTL.Identifier("panic-button-delete-tabs-and-windows"),
+			value=REPLACE(
+				"browser/chrome/browser/browser.dtd",
+				"panicButton.view.deleteTabsAndWindows",
+				{
+					"html:strong>": FTL.TextElement('strong>')
+				}
+			)
+		)
+])