diff --git a/.changeset/stream-merge-left-right.md b/.changeset/stream-merge-left-right.md
new file mode 100644
index 0000000000..7f04d2aef9
--- /dev/null
+++ b/.changeset/stream-merge-left-right.md
@@ -0,0 +1,7 @@
+---
+"effect": minor
+---
+
+refactor(Stream/mergeLeft): rename `self`/`that` argument names to `left`/`right` for clarity
+
+refactor(Stream/mergeRight): rename `self`/`that` argument names to `left`/`right` for clarity
diff --git a/packages/effect/src/Stream.ts b/packages/effect/src/Stream.ts
index 2c996694ab..798321d434 100644
--- a/packages/effect/src/Stream.ts
+++ b/packages/effect/src/Stream.ts
@@ -2232,8 +2232,8 @@ export const mergeEither: {
  * @category utils
  */
 export const mergeLeft: {
-  <A2, E2, R2>(that: Stream<A2, E2, R2>): <A, E, R>(self: Stream<A, E, R>) => Stream<A, E2 | E, R2 | R>
-  <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A, E | E2, R | R2>
+  <AR, ER, RR>(right: Stream<AR, ER, RR>): <AL, EL, RL>(left: Stream<AL, EL, RL>) => Stream<AL, ER | EL, RR | RL>
+  <AL, EL, RL, AR, ER, RR>(left: Stream<AL, EL, RL>, right: Stream<AR, ER, RR>): Stream<AL, EL | ER, RL | RR>
 } = internal.mergeLeft
 
 /**
@@ -2244,8 +2244,8 @@ export const mergeLeft: {
  * @category utils
  */
 export const mergeRight: {
-  <A2, E2, R2>(that: Stream<A2, E2, R2>): <A, E, R>(self: Stream<A, E, R>) => Stream<A2, E2 | E, R2 | R>
-  <A, E, R, A2, E2, R2>(self: Stream<A, E, R>, that: Stream<A2, E2, R2>): Stream<A2, E | E2, R | R2>
+  <AR, ER, RR>(right: Stream<AR, ER, RR>): <AL, EL, RL>(left: Stream<AL, EL, RL>) => Stream<AR, ER | EL, RR | RL>
+  <AL, EL, RL, AR, ER, RR>(left: Stream<AL, EL, RL>, right: Stream<AR, ER, RR>): Stream<AR, EL | ER, RL | RR>
 } = internal.mergeRight
 
 /**
diff --git a/packages/effect/src/internal/stream.ts b/packages/effect/src/internal/stream.ts
index 9fd8aa29cf..96bb5ce5fc 100644
--- a/packages/effect/src/internal/stream.ts
+++ b/packages/effect/src/internal/stream.ts
@@ -3921,36 +3921,36 @@ export const mergeEither = dual<
 
 /** @internal */
 export const mergeLeft = dual<
-  <A2, E2, R2>(
-    that: Stream.Stream<A2, E2, R2>
-  ) => <A, E, R>(self: Stream.Stream<A, E, R>) => Stream.Stream<A, E2 | E, R2 | R>,
-  <A, E, R, A2, E2, R2>(
-    self: Stream.Stream<A, E, R>,
-    that: Stream.Stream<A2, E2, R2>
-  ) => Stream.Stream<A, E2 | E, R2 | R>
+  <AR, ER, RR>(
+    right: Stream.Stream<AR, ER, RR>
+  ) => <AL, EL, RL>(left: Stream.Stream<AL, EL, RL>) => Stream.Stream<AL, ER | EL, RR | RL>,
+  <AL, EL, RL, AR, ER, RR>(
+    left: Stream.Stream<AL, EL, RL>,
+    right: Stream.Stream<AR, ER, RR>
+  ) => Stream.Stream<AL, ER | EL, RR | RL>
 >(
   2,
-  <A, E, R, A2, E2, R2>(
-    self: Stream.Stream<A, E, R>,
-    that: Stream.Stream<A2, E2, R2>
-  ): Stream.Stream<A, E | E2, R | R2> => pipe(self, merge(drain(that)))
+  <AL, EL, RL, AR, ER, RR>(
+    left: Stream.Stream<AL, EL, RL>,
+    right: Stream.Stream<AR, ER, RR>
+  ): Stream.Stream<AL, EL | ER, RL | RR> => pipe(left, merge(drain(right)))
 )
 
 /** @internal */
 export const mergeRight = dual<
-  <A2, E2, R2>(
-    that: Stream.Stream<A2, E2, R2>
-  ) => <A, E, R>(self: Stream.Stream<A, E, R>) => Stream.Stream<A2, E2 | E, R2 | R>,
-  <A, E, R, A2, E2, R2>(
-    self: Stream.Stream<A, E, R>,
-    that: Stream.Stream<A2, E2, R2>
-  ) => Stream.Stream<A2, E2 | E, R2 | R>
+  <AR, ER, RR>(
+    right: Stream.Stream<AR, ER, RR>
+  ) => <AL, EL, RL>(left: Stream.Stream<AL, EL, RL>) => Stream.Stream<AR, ER | EL, RR | RL>,
+  <AL, EL, RL, AR, ER, RR>(
+    left: Stream.Stream<AL, EL, RL>,
+    right: Stream.Stream<AR, ER, RR>
+  ) => Stream.Stream<AR, ER | EL, RR | RL>
 >(
   2,
-  <A, E, R, A2, E2, R2>(
-    self: Stream.Stream<A, E, R>,
-    that: Stream.Stream<A2, E2, R2>
-  ): Stream.Stream<A2, E | E2, R | R2> => pipe(drain(self), merge(that))
+  <AL, EL, RL, AR, ER, RR>(
+    left: Stream.Stream<AL, EL, RL>,
+    right: Stream.Stream<AR, ER, RR>
+  ): Stream.Stream<AR, EL | ER, RL | RR> => pipe(drain(left), merge(right))
 )
 
 /** @internal */