diff --git a/src/services/outliningElementsCollector.ts b/src/services/outliningElementsCollector.ts
index 91754e2ac76..bae6bc7222c 100644
--- a/src/services/outliningElementsCollector.ts
+++ b/src/services/outliningElementsCollector.ts
@@ -63,7 +63,7 @@ namespace ts.OutliningElementsCollector {
             const currentLineStart = lineStarts[i];
             const lineEnd = i + 1 === lineStarts.length ? sourceFile.getEnd() : lineStarts[i + 1] - 1;
             const lineText = sourceFile.text.substring(currentLineStart, lineEnd);
-            const result = lineText.match(/^\s*\/\/\s*#(end)?region(?:\s+(.*))?(?:\r)?$/);
+            const result = isRegionDelimiter(lineText);
             if (!result || isInComment(sourceFile, currentLineStart)) {
                 continue;
             }
@@ -83,16 +83,30 @@ namespace ts.OutliningElementsCollector {
         }
     }
 
+    const regionDelimiterRegExp = /^\s*\/\/\s*#(end)?region(?:\s+(.*))?(?:\r)?$/;
+    function isRegionDelimiter(lineText: string) {
+        return regionDelimiterRegExp.exec(lineText);
+    }
+
     function addOutliningForLeadingCommentsForNode(n: Node, sourceFile: SourceFile, cancellationToken: CancellationToken, out: Push<OutliningSpan>): void {
         const comments = getLeadingCommentRangesOfNode(n, sourceFile);
         if (!comments) return;
         let firstSingleLineCommentStart = -1;
         let lastSingleLineCommentEnd = -1;
         let singleLineCommentCount = 0;
+        const sourceText = sourceFile.getFullText();
         for (const { kind, pos, end } of comments) {
             cancellationToken.throwIfCancellationRequested();
             switch (kind) {
                 case SyntaxKind.SingleLineCommentTrivia:
+                    // never fold region delimiters into single-line comment regions
+                    const commentText = sourceText.slice(pos, end);
+                    if (isRegionDelimiter(commentText)) {
+                        combineAndAddMultipleSingleLineComments();
+                        singleLineCommentCount = 0;
+                        break;
+                    }
+
                     // For single line comments, combine consecutive ones (2 or more) into
                     // a single span from the start of the first till the end of the last
                     if (singleLineCommentCount === 0) {
diff --git a/tests/cases/fourslash/server/getOutliningSpansForRegionsNoSingleLineFolds.ts b/tests/cases/fourslash/server/getOutliningSpansForRegionsNoSingleLineFolds.ts
new file mode 100644
index 00000000000..c2ee165e919
--- /dev/null
+++ b/tests/cases/fourslash/server/getOutliningSpansForRegionsNoSingleLineFolds.ts
@@ -0,0 +1,17 @@
+////[|//#region
+////function foo()[| {
+////
+////}|]
+////[|//these
+//////should|]
+//////#endregion not you|]
+////[|// be
+////// together|]
+////
+////[|//#region bla bla bla
+////
+////function bar()[| { }|]
+////
+//////#endregion|]
+
+verify.outliningSpansInCurrentFile(test.ranges());
\ No newline at end of file