diff --git a/docs/source/features/shortcuts.rst b/docs/source/features/shortcuts.rst
index 0a29927b..e5811c85 100644
--- a/docs/source/features/shortcuts.rst
+++ b/docs/source/features/shortcuts.rst
@@ -101,6 +101,7 @@ Text Formatting Shortcuts
    ":kbd:`Ctrl+B`",       "Format selected text, or word under cursor, with bold"
    ":kbd:`Ctrl+D`",       "Format selected text, or word under cursor, with strike through"
    ":kbd:`Ctrl+I`",       "Format selected text, or word under cursor, with italic"
+   ":kbd:`Ctrl+M`",       "Highlight selected text, or word under cursor"
    ":kbd:`Ctrl+Shift+/`", "Remove format for block or selected text"
    ":kbd:`Ctrl+Shift+D`", "Toggle ignored text format for block or selected text"
 
diff --git a/novelwriter/enum.py b/novelwriter/enum.py
index 18899295..9e50620e 100644
--- a/novelwriter/enum.py
+++ b/novelwriter/enum.py
@@ -92,35 +92,36 @@ class nwDocAction(Enum):
     MD_ITALIC = 6
     MD_BOLD   = 7
     MD_STRIKE = 8
-    S_QUOTE   = 9
-    D_QUOTE   = 10
-    SEL_ALL   = 11
-    SEL_PARA  = 12
-    BLOCK_H1  = 13
-    BLOCK_H2  = 14
-    BLOCK_H3  = 15
-    BLOCK_H4  = 16
-    BLOCK_COM = 17
-    BLOCK_IGN = 18
-    BLOCK_TXT = 19
-    BLOCK_TTL = 20
-    BLOCK_UNN = 21
-    BLOCK_HSC = 22
-    REPL_SNG  = 23
-    REPL_DBL  = 24
-    RM_BREAKS = 25
-    ALIGN_L   = 26
-    ALIGN_C   = 27
-    ALIGN_R   = 28
-    INDENT_L  = 29
-    INDENT_R  = 30
-    SC_ITALIC = 31
-    SC_BOLD   = 32
-    SC_STRIKE = 33
-    SC_ULINE  = 34
-    SC_MARK   = 35
-    SC_SUP    = 36
-    SC_SUB    = 37
+    MD_MARK   = 9
+    S_QUOTE   = 10
+    D_QUOTE   = 11
+    SEL_ALL   = 12
+    SEL_PARA  = 13
+    BLOCK_H1  = 14
+    BLOCK_H2  = 15
+    BLOCK_H3  = 16
+    BLOCK_H4  = 17
+    BLOCK_COM = 18
+    BLOCK_IGN = 19
+    BLOCK_TXT = 20
+    BLOCK_TTL = 21
+    BLOCK_UNN = 22
+    BLOCK_HSC = 23
+    REPL_SNG  = 24
+    REPL_DBL  = 25
+    RM_BREAKS = 26
+    ALIGN_L   = 27
+    ALIGN_C   = 28
+    ALIGN_R   = 29
+    INDENT_L  = 30
+    INDENT_R  = 31
+    SC_ITALIC = 32
+    SC_BOLD   = 33
+    SC_STRIKE = 34
+    SC_ULINE  = 35
+    SC_MARK   = 36
+    SC_SUP    = 37
+    SC_SUB    = 38
 
 
 class nwDocInsert(Enum):
diff --git a/novelwriter/gui/doceditor.py b/novelwriter/gui/doceditor.py
index 5e49d67e..9f0f7bfd 100644
--- a/novelwriter/gui/doceditor.py
+++ b/novelwriter/gui/doceditor.py
@@ -286,6 +286,7 @@ class GuiDocEditor(QPlainTextEdit):
         self.docHeader.clearHeader()
         self.docFooter.setHandle(self._docHandle)
         self.docToolBar.setVisible(False)
+        self.setExtraSelections([])
 
         self.itemHandleChanged.emit("")
 
@@ -742,6 +743,8 @@ class GuiDocEditor(QPlainTextEdit):
             self._toggleFormat(2, "*")
         elif action == nwDocAction.MD_STRIKE:
             self._toggleFormat(2, "~")
+        elif action == nwDocAction.MD_MARK:
+            self._toggleFormat(2, "=")
         elif action == nwDocAction.S_QUOTE:
             self._wrapSelection(CONFIG.fmtSQuoteOpen, CONFIG.fmtSQuoteClose)
         elif action == nwDocAction.D_QUOTE:
@@ -2418,6 +2421,12 @@ class GuiDocToolBar(QWidget):
             qtLambda(self.requestDocAction.emit, nwDocAction.MD_STRIKE)
         )
 
+        self.tbMarkMD = NIconToolButton(self, iSz)
+        self.tbMarkMD.setToolTip(self.tr("Markdown Highlight"))
+        self.tbMarkMD.clicked.connect(
+            qtLambda(self.requestDocAction.emit, nwDocAction.MD_MARK)
+        )
+
         self.tbBold = NIconToolButton(self, iSz)
         self.tbBold.setToolTip(self.tr("Shortcode Bold"))
         self.tbBold.clicked.connect(
@@ -2467,6 +2476,7 @@ class GuiDocToolBar(QWidget):
         self.outerBox.addWidget(self.tbBoldMD)
         self.outerBox.addWidget(self.tbItalicMD)
         self.outerBox.addWidget(self.tbStrikeMD)
+        self.outerBox.addWidget(self.tbMarkMD)
         self.outerBox.addSpacing(4)
         self.outerBox.addWidget(self.tbBold)
         self.outerBox.addWidget(self.tbItalic)
@@ -2501,6 +2511,7 @@ class GuiDocToolBar(QWidget):
         self.tbBoldMD.setThemeIcon("fmt_bold", "orange")
         self.tbItalicMD.setThemeIcon("fmt_italic", "orange")
         self.tbStrikeMD.setThemeIcon("fmt_strike", "orange")
+        self.tbMarkMD.setThemeIcon("fmt_mark", "orange")
         self.tbBold.setThemeIcon("fmt_bold")
         self.tbItalic.setThemeIcon("fmt_italic")
         self.tbStrike.setThemeIcon("fmt_strike")
diff --git a/novelwriter/gui/mainmenu.py b/novelwriter/gui/mainmenu.py
index 33f97dde..3d0ab1c5 100644
--- a/novelwriter/gui/mainmenu.py
+++ b/novelwriter/gui/mainmenu.py
@@ -675,6 +675,14 @@ class GuiMainMenu(QMenuBar):
         )
         self.mainGui.addAction(self.aFmtStrike)
 
+        # Format > Highlight
+        self.aFmtMark = qtAddAction(self.fmtMenu, self.tr("Highlight"))
+        self.aFmtMark.setShortcut("Ctrl+M")
+        self.aFmtMark.triggered.connect(
+            lambda: self.requestDocAction.emit(nwDocAction.MD_MARK)
+        )
+        self.mainGui.addAction(self.aFmtStrike)
+
         # Edit > Separator
         self.fmtMenu.addSeparator()
 
diff --git a/tests/test_gui/test_gui_doceditor.py b/tests/test_gui/test_gui_doceditor.py
index 5bda2d82..ea8f86dd 100644
--- a/tests/test_gui/test_gui_doceditor.py
+++ b/tests/test_gui/test_gui_doceditor.py
@@ -674,9 +674,16 @@ def testGuiEditor_Actions(qtbot, nwGUI, projPath, ipsumText, mockRnd):
     assert docEditor.docAction(nwDocAction.UNDO) is True
     assert docEditor.getText() == text
 
+    # Mark
+    docEditor.setCursorPosition(50)
+    assert docEditor.docAction(nwDocAction.MD_MARK) is True
+    assert docEditor.getText() == text.replace("consectetur", "==consectetur==")
+    assert docEditor.docAction(nwDocAction.UNDO) is True
+    assert docEditor.getText() == text
+
     # Redo
     assert docEditor.docAction(nwDocAction.REDO) is True
-    assert docEditor.getText() == text.replace("consectetur", "~~consectetur~~")
+    assert docEditor.getText() == text.replace("consectetur", "==consectetur==")
     assert docEditor.docAction(nwDocAction.UNDO) is True
     assert docEditor.getText() == text