diff --git a/.changelog/4828.fixed b/.changelog/4828.fixed
new file mode 100644
index 0000000000..693d029d24
--- /dev/null
+++ b/.changelog/4828.fixed
@@ -0,0 +1 @@
+`opentelemetry-instrumentation-redis`: treat explicit `db=None` as database index 0
diff --git a/instrumentation/opentelemetry-instrumentation-redis/src/opentelemetry/instrumentation/redis/util.py b/instrumentation/opentelemetry-instrumentation-redis/src/opentelemetry/instrumentation/redis/util.py
index c8a5692510..9a99a150ab 100644
--- a/instrumentation/opentelemetry-instrumentation-redis/src/opentelemetry/instrumentation/redis/util.py
+++ b/instrumentation/opentelemetry-instrumentation-redis/src/opentelemetry/instrumentation/redis/util.py
@@ -45,7 +45,11 @@ def _extract_conn_attributes(
         attributes, DbSystemValues.REDIS.value, db_sem_conv_opt_in_mode
     )
 
+    # redis-py may pass db=None explicitly (e.g. from_url); treat that as 0.
+    # dict.get("db", 0) only defaults when the key is missing, not when it is None.
     db = conn_kwargs.get("db", 0)
+    if db is None:
+        db = 0
     _set_db_redis_database_index(attributes, db, db_sem_conv_opt_in_mode)
     if "path" in conn_kwargs:
         _set_http_net_peer_name_client(
@@ -144,6 +148,8 @@ def _build_span_name(
             name = cmd_args[0]
     else:
         name = instance.connection_pool.connection_kwargs.get("db", 0)
+        if name is None:
+            name = 0
     return name
 
 
diff --git a/instrumentation/opentelemetry-instrumentation-redis/tests/test_redis.py b/instrumentation/opentelemetry-instrumentation-redis/tests/test_redis.py
index d91a9e6a15..71ca51c3a8 100644
--- a/instrumentation/opentelemetry-instrumentation-redis/tests/test_redis.py
+++ b/instrumentation/opentelemetry-instrumentation-redis/tests/test_redis.py
@@ -351,6 +351,24 @@ def test_attributes_default(self):
             NetTransportValues.IP_TCP.value,
         )
 
+    def test_attributes_db_none(self):
+        """db=None in connection kwargs should default to index 0 (issue #1905)."""
+        redis_client = redis.Redis()
+        redis_client.connection_pool.connection_kwargs["db"] = None
+
+        with mock.patch.object(redis_client, "connection"):
+            redis_client.set("key", "value")
+
+        spans = self.memory_exporter.get_finished_spans()
+        self.assertEqual(len(spans), 1)
+
+        span = spans[0]
+        self.assertEqual(span.attributes[DB_REDIS_DATABASE_INDEX], 0)
+        self.assertEqual(
+            span.attributes[DB_SYSTEM],
+            DbSystemValues.REDIS.value,
+        )
+
     def test_attributes_tcp(self):
         redis_client = redis.Redis.from_url("redis://foo:bar@1.1.1.1:6380/1")