diff --git a/README.md b/README.md
index 16fc8f0e..3d44d0e1 100644
--- a/README.md
+++ b/README.md
@@ -78,7 +78,7 @@ Now visiting http://localhost:8001/History/downloads will show you a web interfa
       --plugins-dir DIRECTORY   Path to directory containing custom plugins
       --static STATIC MOUNT     mountpoint:path-to-directory for serving static
                                 files
-      --memory                  Make :memory: database available
+      --memory                  Make /_memory database available
       --config CONFIG           Set config option using configname:value
                                 docs.datasette.io/en/stable/config.html
       --version-note TEXT       Additional note to show on /-/versions
diff --git a/datasette/app.py b/datasette/app.py
index cfce8e0b..9e15a162 100644
--- a/datasette/app.py
+++ b/datasette/app.py
@@ -218,7 +218,7 @@ class Datasette:
         self.immutables = set(immutables or [])
         self.databases = collections.OrderedDict()
         if memory or not self.files:
-            self.add_database(Database(self, is_memory=True), name=":memory:")
+            self.add_database(Database(self, is_memory=True), name="_memory")
         # memory_name is a random string so that each Datasette instance gets its own
         # unique in-memory named database - otherwise unit tests can fail with weird
         # errors when different instances accidentally share an in-memory database
@@ -633,7 +633,7 @@ class Datasette:
 
     def _versions(self):
         conn = sqlite3.connect(":memory:")
-        self._prepare_connection(conn, ":memory:")
+        self._prepare_connection(conn, "_memory")
         sqlite_version = conn.execute("select sqlite_version()").fetchone()[0]
         sqlite_extensions = {}
         for extension, testsql, hasversion in (
@@ -927,6 +927,12 @@ class Datasette:
                         plugin["name"].replace("-", "_")
                     ),
                 )
+        add_route(
+            permanent_redirect(
+                "/_memory", forward_query_string=True, forward_rest=True
+            ),
+            r"/:memory:(?P<rest>.*)$",
+        )
         add_route(
             JsonDataView.as_view(self, "metadata.json", lambda: self._metadata),
             r"/-/metadata(?P<as_format>(\.json)?)$",
@@ -1290,9 +1296,18 @@ def wrap_view(view_fn, datasette):
     return async_view_fn
 
 
-def permanent_redirect(path):
+def permanent_redirect(path, forward_query_string=False, forward_rest=False):
     return wrap_view(
-        lambda request, send: Response.redirect(path, status=301),
+        lambda request, send: Response.redirect(
+            path
+            + (request.url_vars["rest"] if forward_rest else "")
+            + (
+                ("?" + request.query_string)
+                if forward_query_string and request.query_string
+                else ""
+            ),
+            status=301,
+        ),
         datasette=None,
     )
 
diff --git a/datasette/cli.py b/datasette/cli.py
index eade19a0..25d6acea 100644
--- a/datasette/cli.py
+++ b/datasette/cli.py
@@ -365,7 +365,7 @@ def uninstall(packages, yes):
     help="Serve static files from this directory at /MOUNT/...",
     multiple=True,
 )
-@click.option("--memory", is_flag=True, help="Make :memory: database available")
+@click.option("--memory", is_flag=True, help="Make /_memory database available")
 @click.option(
     "--config",
     type=Config(),
diff --git a/datasette/views/database.py b/datasette/views/database.py
index f6fd579c..75eb8f02 100644
--- a/datasette/views/database.py
+++ b/datasette/views/database.py
@@ -138,7 +138,7 @@ class DatabaseView(DataView):
                 "metadata": metadata,
                 "allow_download": self.ds.setting("allow_download")
                 and not db.is_mutable
-                and database != ":memory:",
+                and not db.is_memory,
             },
             (f"database-{to_css_class(database)}.html", "database.html"),
         )
@@ -160,7 +160,7 @@ class DatabaseDownload(DataView):
             raise DatasetteError("Invalid database", status=404)
         db = self.ds.databases[database]
         if db.is_memory:
-            raise DatasetteError("Cannot download :memory: database", status=404)
+            raise DatasetteError("Cannot download in-memory databases", status=404)
         if not self.ds.setting("allow_download") or db.is_mutable:
             raise Forbidden("Database download is forbidden")
         if not db.path:
diff --git a/docs/datasette-serve-help.txt b/docs/datasette-serve-help.txt
index 079ec9f8..257d38c6 100644
--- a/docs/datasette-serve-help.txt
+++ b/docs/datasette-serve-help.txt
@@ -24,7 +24,7 @@ Options:
   --template-dir DIRECTORY  Path to directory containing custom templates
   --plugins-dir DIRECTORY   Path to directory containing custom plugins
   --static MOUNT:DIRECTORY  Serve static files from this directory at /MOUNT/...
-  --memory                  Make :memory: database available
+  --memory                  Make /_memory database available
   --config CONFIG           Deprecated: set config option using configname:value. Use
                             --setting instead.
 
diff --git a/tests/test_api.py b/tests/test_api.py
index 0d1bddd3..0b5401d6 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -608,11 +608,11 @@ def test_no_files_uses_memory_database(app_client_no_files):
     response = app_client_no_files.get("/.json")
     assert response.status == 200
     assert {
-        ":memory:": {
-            "name": ":memory:",
+        "_memory": {
+            "name": "_memory",
             "hash": None,
-            "color": "f7935d",
-            "path": "/%3Amemory%3A",
+            "color": "a6c7b9",
+            "path": "/_memory",
             "tables_and_views_truncated": [],
             "tables_and_views_more": False,
             "tables_count": 0,
@@ -626,12 +626,28 @@ def test_no_files_uses_memory_database(app_client_no_files):
     } == response.json
     # Try that SQL query
     response = app_client_no_files.get(
-        "/:memory:.json?sql=select+sqlite_version()&_shape=array"
+        "/_memory.json?sql=select+sqlite_version()&_shape=array"
     )
     assert 1 == len(response.json)
     assert ["sqlite_version()"] == list(response.json[0].keys())
 
 
+@pytest.mark.parametrize(
+    "path,expected_redirect",
+    (
+        ("/:memory:", "/_memory"),
+        ("/:memory:.json", "/_memory.json"),
+        ("/:memory:?sql=select+1", "/_memory?sql=select+1"),
+        ("/:memory:.json?sql=select+1", "/_memory.json?sql=select+1"),
+        ("/:memory:.csv?sql=select+1", "/_memory.csv?sql=select+1"),
+    ),
+)
+def test_old_memory_urls_redirect(app_client_no_files, path, expected_redirect):
+    response = app_client_no_files.get(path, allow_redirects=False)
+    assert response.status == 301
+    assert response.headers["location"] == expected_redirect
+
+
 def test_database_page_for_database_with_dot_in_name(app_client_with_dot):
     response = app_client_with_dot.get("/fixtures.dot.json")
     assert 200 == response.status
diff --git a/tests/test_cli.py b/tests/test_cli.py
index c42c22ea..33c2c8ac 100644
--- a/tests/test_cli.py
+++ b/tests/test_cli.py
@@ -221,7 +221,7 @@ def test_config_deprecated(ensure_eventloop):
 
 def test_sql_errors_logged_to_stderr(ensure_eventloop):
     runner = CliRunner(mix_stderr=False)
-    result = runner.invoke(cli, ["--get", "/:memory:.json?sql=select+blah"])
+    result = runner.invoke(cli, ["--get", "/_memory.json?sql=select+blah"])
     assert result.exit_code == 1
     assert "sql = 'select blah', params = {}: no such column: blah\n" in result.stderr
 
diff --git a/tests/test_cli_serve_get.py b/tests/test_cli_serve_get.py
index 39236dd8..aaa692e5 100644
--- a/tests/test_cli_serve_get.py
+++ b/tests/test_cli_serve_get.py
@@ -30,12 +30,12 @@ def test_serve_with_get(tmp_path_factory):
             "--plugins-dir",
             str(plugins_dir),
             "--get",
-            "/:memory:.json?sql=select+sqlite_version()",
+            "/_memory.json?sql=select+sqlite_version()",
         ],
     )
     assert 0 == result.exit_code, result.output
     assert {
-        "database": ":memory:",
+        "database": "_memory",
         "truncated": False,
         "columns": ["sqlite_version()"],
     }.items() <= json.loads(result.output).items()
diff --git a/tests/test_html.py b/tests/test_html.py
index 6c33fba7..9f7a987d 100644
--- a/tests/test_html.py
+++ b/tests/test_html.py
@@ -88,7 +88,7 @@ def test_static_mounts():
 
 def test_memory_database_page():
     with make_app_client(memory=True) as client:
-        response = client.get("/:memory:")
+        response = client.get("/_memory")
         assert response.status == 200
 
 
@@ -1056,10 +1056,10 @@ def test_database_download_disallowed_for_mutable(app_client):
 def test_database_download_disallowed_for_memory():
     with make_app_client(memory=True) as client:
         # Memory page should NOT have a download link
-        response = client.get("/:memory:")
+        response = client.get("/_memory")
         soup = Soup(response.body, "html.parser")
         assert 0 == len(soup.findAll("a", {"href": re.compile(r"\.db$")}))
-        assert 404 == client.get("/:memory:.db").status
+        assert 404 == client.get("/_memory.db").status
 
 
 def test_allow_download_off():
diff --git a/tests/test_internals_urls.py b/tests/test_internals_urls.py
index e6f405b3..e486e4c9 100644
--- a/tests/test_internals_urls.py
+++ b/tests/test_internals_urls.py
@@ -103,14 +103,14 @@ def test_logout(ds, base_url, expected):
 @pytest.mark.parametrize(
     "base_url,format,expected",
     [
-        ("/", None, "/%3Amemory%3A"),
-        ("/prefix/", None, "/prefix/%3Amemory%3A"),
-        ("/", "json", "/%3Amemory%3A.json"),
+        ("/", None, "/_memory"),
+        ("/prefix/", None, "/prefix/_memory"),
+        ("/", "json", "/_memory.json"),
     ],
 )
 def test_database(ds, base_url, format, expected):
     ds._settings["base_url"] = base_url
-    actual = ds.urls.database(":memory:", format=format)
+    actual = ds.urls.database("_memory", format=format)
     assert actual == expected
     assert isinstance(actual, PrefixedUrlString)
 
@@ -118,18 +118,18 @@ def test_database(ds, base_url, format, expected):
 @pytest.mark.parametrize(
     "base_url,name,format,expected",
     [
-        ("/", "name", None, "/%3Amemory%3A/name"),
-        ("/prefix/", "name", None, "/prefix/%3Amemory%3A/name"),
-        ("/", "name", "json", "/%3Amemory%3A/name.json"),
-        ("/", "name.json", "json", "/%3Amemory%3A/name.json?_format=json"),
+        ("/", "name", None, "/_memory/name"),
+        ("/prefix/", "name", None, "/prefix/_memory/name"),
+        ("/", "name", "json", "/_memory/name.json"),
+        ("/", "name.json", "json", "/_memory/name.json?_format=json"),
     ],
 )
 def test_table_and_query(ds, base_url, name, format, expected):
     ds._settings["base_url"] = base_url
-    actual1 = ds.urls.table(":memory:", name, format=format)
+    actual1 = ds.urls.table("_memory", name, format=format)
     assert actual1 == expected
     assert isinstance(actual1, PrefixedUrlString)
-    actual2 = ds.urls.query(":memory:", name, format=format)
+    actual2 = ds.urls.query("_memory", name, format=format)
     assert actual2 == expected
     assert isinstance(actual2, PrefixedUrlString)
 
@@ -137,14 +137,14 @@ def test_table_and_query(ds, base_url, name, format, expected):
 @pytest.mark.parametrize(
     "base_url,format,expected",
     [
-        ("/", None, "/%3Amemory%3A/facetable/1"),
-        ("/prefix/", None, "/prefix/%3Amemory%3A/facetable/1"),
-        ("/", "json", "/%3Amemory%3A/facetable/1.json"),
+        ("/", None, "/_memory/facetable/1"),
+        ("/prefix/", None, "/prefix/_memory/facetable/1"),
+        ("/", "json", "/_memory/facetable/1.json"),
     ],
 )
 def test_row(ds, base_url, format, expected):
     ds._settings["base_url"] = base_url
-    actual = ds.urls.row(":memory:", "facetable", "1", format=format)
+    actual = ds.urls.row("_memory", "facetable", "1", format=format)
     assert actual == expected
     assert isinstance(actual, PrefixedUrlString)