diff --git a/django/contrib/admin/static/admin/css/forms.css b/django/contrib/admin/static/admin/css/forms.css
index 77985d5d34..82930a0cd6 100644
--- a/django/contrib/admin/static/admin/css/forms.css
+++ b/django/contrib/admin/static/admin/css/forms.css
@@ -177,7 +177,7 @@ form .aligned table p {
     padding-left: 0;
 }
 
-fieldset .field-box {
+fieldset .fieldBox {
     float: left;
     margin-right: 20px;
 }
diff --git a/django/contrib/admin/static/admin/css/responsive.css b/django/contrib/admin/static/admin/css/responsive.css
index 7460304843..2a4b2bbd40 100644
--- a/django/contrib/admin/static/admin/css/responsive.css
+++ b/django/contrib/admin/static/admin/css/responsive.css
@@ -207,13 +207,13 @@ input[type="submit"], button {
         min-height: 0;
     }
 
-    fieldset .field-box {
+    fieldset .fieldBox {
         float: none;
         margin: 0 -10px;
         padding: 0 10px;
     }
 
-    fieldset .field-box + .field-box {
+    fieldset .fieldBox + .fieldBox {
         margin-top: 10px;
         padding-top: 10px;
         border-top: 1px solid #eee;
@@ -572,7 +572,7 @@ input[type="submit"], button {
         width: auto;
     }
 
-    fieldset .field-box + .field-box {
+    fieldset .fieldBox + .fieldBox {
         margin-top: 15px;
         padding-top: 15px;
     }
diff --git a/django/contrib/admin/static/admin/css/rtl.css b/django/contrib/admin/static/admin/css/rtl.css
index ef397815e6..f7514a5d38 100644
--- a/django/contrib/admin/static/admin/css/rtl.css
+++ b/django/contrib/admin/static/admin/css/rtl.css
@@ -180,7 +180,7 @@ input[type=submit].default, .submit-row input.default {
     float: left;
 }
 
-fieldset .field-box {
+fieldset .fieldBox {
     float: right;
     margin-left: 20px;
     margin-right: 0;
diff --git a/django/contrib/admin/templates/admin/includes/fieldset.html b/django/contrib/admin/templates/admin/includes/fieldset.html
index fce9966664..218fd5a4c1 100644
--- a/django/contrib/admin/templates/admin/includes/fieldset.html
+++ b/django/contrib/admin/templates/admin/includes/fieldset.html
@@ -7,7 +7,7 @@
         <div class="form-row{% if line.fields|length_is:'1' and line.errors %} errors{% endif %}{% if not line.has_visible_field %} hidden{% endif %}{% for field in line %}{% if field.field.name %} field-{{ field.field.name }}{% endif %}{% endfor %}">
             {% if line.fields|length_is:'1' %}{{ line.errors }}{% endif %}
             {% for field in line %}
-                <div{% if not line.fields|length_is:'1' %} class="field-box{% if field.field.name %} field-{{ field.field.name }}{% endif %}{% if not field.is_readonly and field.errors %} errors{% endif %}{% if field.field.is_hidden %} hidden{% endif %}"{% elif field.is_checkbox %} class="checkbox-row"{% endif %}>
+                <div{% if not line.fields|length_is:'1' %} class="fieldBox{% if field.field.name %} field-{{ field.field.name }}{% endif %}{% if not field.is_readonly and field.errors %} errors{% endif %}{% if field.field.is_hidden %} hidden{% endif %}"{% elif field.is_checkbox %} class="checkbox-row"{% endif %}>
                     {% if not line.fields|length_is:'1' and not field.is_readonly %}{{ field.errors }}{% endif %}
                     {% if field.is_checkbox %}
                         {{ field.field }}{{ field.label_tag }}
diff --git a/docs/releases/2.1.txt b/docs/releases/2.1.txt
index f41d5178fa..d7737e486a 100644
--- a/docs/releases/2.1.txt
+++ b/docs/releases/2.1.txt
@@ -380,6 +380,9 @@ Miscellaneous
   value now matches objects that have the specified key and a null value rather
   than objects that don't have the key.
 
+* The admin CSS class ``field-box`` is renamed to ``fieldBox`` to prevent
+  conflicts with the class given to model fields named "box".
+
 .. _deprecated-features-2.1:
 
 Features deprecated in 2.1
diff --git a/tests/admin_views/tests.py b/tests/admin_views/tests.py
index 1d49c789ec..e2421cb31a 100644
--- a/tests/admin_views/tests.py
+++ b/tests/admin_views/tests.py
@@ -5706,10 +5706,10 @@ class TestLabelVisibility(TestCase):
         self.assert_field_visible(response, 'second')
 
     def assert_field_visible(self, response, field_name):
-        self.assertContains(response, '<div class="field-box field-%s">' % field_name)
+        self.assertContains(response, '<div class="fieldBox field-%s">' % field_name)
 
     def assert_field_hidden(self, response, field_name):
-        self.assertContains(response, '<div class="field-box field-%s hidden">' % field_name)
+        self.assertContains(response, '<div class="fieldBox field-%s hidden">' % field_name)
 
     def assert_fieldline_visible(self, response):
         self.assertContains(response, '<div class="form-row field-first field-second">')