diff --git a/CHANGELOG.md b/CHANGELOG.md
index c3edd24e4b..a0d7f6f046 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -20,6 +20,7 @@ We use *breaking :warning:* to mark changes that are not backward compatible (re
 - [#7317](https://github.com/thanos-io/thanos/pull/7317) Tracing: allow specifying resource attributes for the OTLP configuration.
 - [#7367](https://github.com/thanos-io/thanos/pull/7367) Store Gateway: log request ID in request logs.
 - [#7361](https://github.com/thanos-io/thanos/pull/7361) Query: *breaking :warning:* pass query stats from remote execution from server to client. We changed the protobuf of the QueryAPI, if you use `query.mode=distributed` you need to update your client (upper level Queriers) first, before updating leaf Queriers (servers).
+- [#7363](https://github.com/thanos-io/thanos/pull/7363) Query-frontend: set value of remote_user field in Slow Query Logs from HTTP header
 
 ### Changed
 
diff --git a/cmd/thanos/query_frontend.go b/cmd/thanos/query_frontend.go
index 78d1ec3744..e60169f103 100644
--- a/cmd/thanos/query_frontend.go
+++ b/cmd/thanos/query_frontend.go
@@ -161,6 +161,8 @@ func registerQueryFrontend(app *extkingpin.App) {
 
 	cmd.Flag("query-frontend.vertical-shards", "Number of shards to use when distributing shardable PromQL queries. For more details, you can refer to the Vertical query sharding proposal: https://thanos.io/tip/proposals-accepted/202205-vertical-query-sharding.md").IntVar(&cfg.NumShards)
 
+	cmd.Flag("query-frontend.slow-query-logs-user-header", "Set the value of the field remote_user in the slow query logs to the value of the given HTTP header. Falls back to reading the user from the basic auth header.").PlaceHolder("<http-header-name>").Default("").StringVar(&cfg.CortexHandlerConfig.SlowQueryLogsUserHeader)
+
 	reqLogConfig := extkingpin.RegisterRequestLoggingFlags(cmd)
 
 	cmd.Setup(func(g *run.Group, logger log.Logger, reg *prometheus.Registry, tracer opentracing.Tracer, _ <-chan struct{}, _ bool) error {
diff --git a/docs/components/query-frontend.md b/docs/components/query-frontend.md
index 8025cdecc8..bb0f68a2fd 100644
--- a/docs/components/query-frontend.md
+++ b/docs/components/query-frontend.md
@@ -157,6 +157,8 @@ Other cache configuration parameters, you can refer to [redis-index-cache](store
 
 Query Frontend supports `--query-frontend.log-queries-longer-than` flag to log queries running longer than some duration.
 
+The field `remote_user` can be read from an HTTP header, like `X-Grafana-User`, by setting `--query-frontend.slow-query-logs-user-header`.
+
 ## Naming
 
 Naming is hard :) Please check [here](https://github.com/thanos-io/thanos/pull/2434#discussion_r408300683) to see why we chose `query-frontend` as the name.
@@ -295,6 +297,11 @@ Flags:
                                  the request, the first matching arg specified
                                  will take precedence. If no headers match
                                  'anonymous' will be used.
+      --query-frontend.slow-query-logs-user-header=<http-header-name>
+                                 Set the value of the field remote_user in the
+                                 slow query logs to the value of the given HTTP
+                                 header. Falls back to reading the user from the
+                                 basic auth header.
       --query-frontend.vertical-shards=QUERY-FRONTEND.VERTICAL-SHARDS
                                  Number of shards to use when
                                  distributing shardable PromQL queries.
diff --git a/internal/cortex/frontend/transport/handler.go b/internal/cortex/frontend/transport/handler.go
index 602a54d027..8c3020a6d9 100644
--- a/internal/cortex/frontend/transport/handler.go
+++ b/internal/cortex/frontend/transport/handler.go
@@ -43,9 +43,10 @@ var (
 
 // Config for a Handler.
 type HandlerConfig struct {
-	LogQueriesLongerThan time.Duration `yaml:"log_queries_longer_than"`
-	MaxBodySize          int64         `yaml:"max_body_size"`
-	QueryStatsEnabled    bool          `yaml:"query_stats_enabled"`
+	LogQueriesLongerThan    time.Duration `yaml:"log_queries_longer_than"`
+	MaxBodySize             int64         `yaml:"max_body_size"`
+	QueryStatsEnabled       bool          `yaml:"query_stats_enabled"`
+	SlowQueryLogsUserHeader string        `yaml:"slow_query_logs_user_header"`
 }
 
 // Handler accepts queries and forwards them to RoundTripper. It can log slow queries,
@@ -176,7 +177,13 @@ func (f *Handler) reportSlowQuery(r *http.Request, responseHeaders http.Header,
 		thanosTraceID = traceID
 	}
 
-	remoteUser, _, _ := r.BasicAuth()
+	var remoteUser string
+	// Prefer reading remote user from header. Fall back to the value of basic authentication.
+	if f.cfg.SlowQueryLogsUserHeader != "" {
+		remoteUser = r.Header.Get(f.cfg.SlowQueryLogsUserHeader)
+	} else {
+		remoteUser, _, _ = r.BasicAuth()
+	}
 
 	logMessage := append([]interface{}{
 		"msg", "slow query detected",