diff --git a/doc/usage/extensions/math.rst b/doc/usage/extensions/math.rst
index 35f283846..9daa03186 100644
--- a/doc/usage/extensions/math.rst
+++ b/doc/usage/extensions/math.rst
@@ -168,6 +168,23 @@ Sphinx.
 
    The default is empty (``{}``).
 
+.. confval:: mathjax_config
+
+   The inline configuration options for mathjax.  The value is used as a
+   parameter of ``MathJax.Hub.Config()``.  For more information, please
+   read `Using in-line configuration options`_.
+
+   For example::
+
+       mathjax_config = {
+           'extensions': ['tex2jax.js'],
+           'jax': ['input/TeX', 'output/HTML-CSS'],
+       }
+
+   The default is empty (not configured).
+
+.. _Using in-line configuration options: http://docs.mathjax.org/en/latest/configuration.html#using-in-line-configuration-options
+
 :mod:`sphinx.ext.jsmath` -- Render math via JavaScript
 ------------------------------------------------------
 
diff --git a/sphinx/builders/html.py b/sphinx/builders/html.py
index f08cb909f..0deaec707 100644
--- a/sphinx/builders/html.py
+++ b/sphinx/builders/html.py
@@ -420,7 +420,7 @@ class StandaloneHTMLBuilder(Builder):
 
     def add_js_file(self, filename, **kwargs):
         # type: (unicode, **unicode) -> None
-        if '://' not in filename:
+        if filename and '://' not in filename:
             filename = posixpath.join('_static', filename)
 
         self.script_files.append(JavaScript(filename, **kwargs))  # type: ignore
@@ -1630,17 +1630,22 @@ def setup_js_tag_helper(app, pagename, templatexname, context, doctree):
     def js_tag(js):
         # type: (JavaScript) -> unicode
         attrs = []
+        body = ''  # type: unicode
         if isinstance(js, JavaScript):
             for key in sorted(js.attributes):
                 value = js.attributes[key]
                 if value is not None:
-                    attrs.append('%s="%s"' % (key, htmlescape(value, True)))
-            attrs.append('src="%s"' % pathto(js.filename, resource=True))
+                    if key == 'body':
+                        body = value
+                    else:
+                        attrs.append('%s="%s"' % (key, htmlescape(value, True)))
+            if js.filename:
+                attrs.append('src="%s"' % pathto(js.filename, resource=True))
         else:
             # str value (old styled)
             attrs.append('type="text/javascript"')
             attrs.append('src="%s"' % pathto(js, resource=True))
-        return '<script %s></script>' % ' '.join(attrs)
+        return '<script %s>%s</script>' % (' '.join(attrs), body)
 
     context['js_tag'] = js_tag
 
diff --git a/sphinx/ext/mathjax.py b/sphinx/ext/mathjax.py
index 20d5866c5..341eb12c8 100644
--- a/sphinx/ext/mathjax.py
+++ b/sphinx/ext/mathjax.py
@@ -11,6 +11,8 @@
     :license: BSD, see LICENSE for details.
 """
 
+import json
+
 from docutils import nodes
 
 import sphinx
@@ -79,6 +81,10 @@ def builder_inited(app):
             options.update(app.config.mathjax_options)
         app.builder.add_js_file(app.config.mathjax_path, **options)  # type: ignore
 
+        if app.config.mathjax_config:
+            body = "MathJax.Hub.Config(%s)" % json.dumps(app.config.mathjax_config)
+            app.builder.add_js_file(None, type="text/x-mathjax-config", body=body)  # type: ignore  # NOQA
+
 
 def setup(app):
     # type: (Sphinx) -> Dict[unicode, Any]
@@ -94,6 +100,7 @@ def setup(app):
     app.add_config_value('mathjax_options', {}, 'html')
     app.add_config_value('mathjax_inline', [r'\(', r'\)'], 'html')
     app.add_config_value('mathjax_display', [r'\[', r'\]'], 'html')
+    app.add_config_value('mathjax_config', None, 'html')
     app.connect('builder-inited', builder_inited)
 
     return {'version': sphinx.__display_version__, 'parallel_read_safe': True}
diff --git a/tests/test_ext_math.py b/tests/test_ext_math.py
index 99940977b..8f24349a4 100644
--- a/tests/test_ext_math.py
+++ b/tests/test_ext_math.py
@@ -249,3 +249,15 @@ def test_math_compat(app, status, warning):
                      [nodes.math_block, "e^{i\\pi}+1=0\n\n"],
                      [nodes.paragraph, "Multi math equations"],
                      [nodes.math_block, "E = mc^2"]))
+
+
+@pytest.mark.sphinx('html', testroot='basic',
+                    confoverrides={'extensions': ['sphinx.ext.mathjax'],
+                                   'mathjax_config': {'extensions': ['tex2jax.js']}})
+def test_mathjax_config(app, status, warning):
+    app.builder.build_all()
+
+    content = (app.outdir / 'index.html').text()
+    assert ('<script type="text/x-mathjax-config">'
+            'MathJax.Hub.Config({"extensions": ["tex2jax.js"]})'
+            '</script>' in content)