diff --git a/packages/reflex-base/news/+referrer-param-env-var.feature.md b/packages/reflex-base/news/+referrer-param-env-var.feature.md
new file mode 100644
index 00000000000..cc89d0fe737
--- /dev/null
+++ b/packages/reflex-base/news/+referrer-param-env-var.feature.md
@@ -0,0 +1 @@
+Add the `REFLEX_REFERRER_PARAM` environment variable, read at compile time to append a `ref` query parameter to the "Built with Reflex" badge link.
diff --git a/packages/reflex-base/src/reflex_base/environment.py b/packages/reflex-base/src/reflex_base/environment.py
index e1556dc6a97..587bba04026 100644
--- a/packages/reflex-base/src/reflex_base/environment.py
+++ b/packages/reflex-base/src/reflex_base/environment.py
@@ -759,6 +759,10 @@ class EnvironmentVariables:
     # Extra plugins to append to the config's plugins list.
     REFLEX_EXTRA_PLUGINS: EnvVar[list[type[Plugin]]] = env_var([])
 
+    # Referrer identifier appended (urlencoded) to the "Built with Reflex"
+    # badge link as https://reflex.dev/?ref=<value>. Read at compile time.
+    REFLEX_REFERRER_PARAM: EnvVar[str | None] = env_var(None)
+
 
 environment = EnvironmentVariables()
 
diff --git a/packages/reflex-components-core/news/+badge-referrer-param.feature.md b/packages/reflex-components-core/news/+badge-referrer-param.feature.md
new file mode 100644
index 00000000000..6e222f7b5ee
--- /dev/null
+++ b/packages/reflex-components-core/news/+badge-referrer-param.feature.md
@@ -0,0 +1 @@
+The "Built with Reflex" badge appends a urlencoded `ref` query parameter to its reflex.dev link when the `REFLEX_REFERRER_PARAM` environment variable is set at compile time.
diff --git a/packages/reflex-components-core/src/reflex_components_core/core/sticky.py b/packages/reflex-components-core/src/reflex_components_core/core/sticky.py
index 3881d77e0dd..f4f7312e341 100644
--- a/packages/reflex-components-core/src/reflex_components_core/core/sticky.py
+++ b/packages/reflex-components-core/src/reflex_components_core/core/sticky.py
@@ -1,6 +1,9 @@
 """Components for displaying the Reflex sticky logo."""
 
+import urllib.parse
+
 from reflex_base.components.component import ComponentNamespace
+from reflex_base.environment import environment
 from reflex_base.style import Style
 
 from reflex_components_core.core.colors import color
@@ -69,6 +72,18 @@ def add_style(self):
         })
 
 
+def _badge_href() -> str:
+    """Compute the badge link, appending the referrer param when set.
+
+    Returns:
+        The badge destination URL.
+    """
+    referrer = environment.REFLEX_REFERRER_PARAM.get()
+    if referrer:
+        return f"https://reflex.dev/?ref={urllib.parse.quote(referrer, safe='')}"
+    return "https://reflex.dev"
+
+
 class StickyBadge(A):
     """A badge that displays the Reflex sticky logo."""
 
@@ -82,7 +97,7 @@ def create(cls):
         return super().create(
             StickyLogo.create(),
             desktop_only(StickyLabel.create()),
-            href="https://reflex.dev",
+            href=_badge_href(),
             target="_blank",
             width="auto",
             padding="0.375rem",
diff --git a/tests/units/components/core/test_sticky.py b/tests/units/components/core/test_sticky.py
new file mode 100644
index 00000000000..257201f2553
--- /dev/null
+++ b/tests/units/components/core/test_sticky.py
@@ -0,0 +1,39 @@
+"""Tests for the "Built with Reflex" sticky badge."""
+
+import pytest
+from reflex_components_core.core.sticky import StickyBadge
+
+
+def _badge_href() -> str:
+    """Render a fresh badge and extract its href prop.
+
+    Returns:
+        The rendered href value, without surrounding quotes.
+    """
+    props = StickyBadge.create().render()["props"]
+    href_prop = next(p for p in props if p.startswith("href:"))
+    return href_prop.removeprefix("href:").strip('"')
+
+
+def test_badge_href_default(monkeypatch: pytest.MonkeyPatch):
+    """Without a referrer param, the badge links to the plain reflex.dev URL."""
+    monkeypatch.delenv("REFLEX_REFERRER_PARAM", raising=False)
+    assert _badge_href() == "https://reflex.dev"
+
+
+def test_badge_href_with_referrer(monkeypatch: pytest.MonkeyPatch):
+    """A referrer param is appended as a ref query parameter."""
+    monkeypatch.setenv("REFLEX_REFERRER_PARAM", "owner-123")
+    assert _badge_href() == "https://reflex.dev/?ref=owner-123"
+
+
+def test_badge_href_urlencodes_referrer(monkeypatch: pytest.MonkeyPatch):
+    """Special characters in the referrer param are urlencoded."""
+    monkeypatch.setenv("REFLEX_REFERRER_PARAM", "a b&c/d?e=f")
+    assert _badge_href() == "https://reflex.dev/?ref=a%20b%26c%2Fd%3Fe%3Df"
+
+
+def test_badge_href_empty_referrer(monkeypatch: pytest.MonkeyPatch):
+    """An empty referrer param falls back to the default URL."""
+    monkeypatch.setenv("REFLEX_REFERRER_PARAM", "")
+    assert _badge_href() == "https://reflex.dev"