diff --git a/compiler/rustc_parse/src/lexer/unescape_error_reporting.rs b/compiler/rustc_parse/src/lexer/unescape_error_reporting.rs
index efa53f0962b78..266cb01d5b534 100644
--- a/compiler/rustc_parse/src/lexer/unescape_error_reporting.rs
+++ b/compiler/rustc_parse/src/lexer/unescape_error_reporting.rs
@@ -158,6 +158,13 @@ pub(crate) fn emit_unescape_error(
                     "this is an isolated carriage return; consider checking your editor and \
                      version control settings",
                 );
+            } else if looks_like_quote(c) {
+                diag.help(format!(
+                    "{ec} is not an ascii quote, \
+                             but may look like one in some fonts.\n\
+                             consider writing it in its \
+                             escaped form for clarity."
+                ));
             } else {
                 if mode == Mode::Str || mode == Mode::Char {
                     diag.span_suggestion(
@@ -295,3 +302,17 @@ pub(crate) fn escaped_char(c: char) -> String {
         _ => c.escape_default().to_string(),
     }
 }
+
+/// Returns true if `c` may look identical to `"` in some fonts.
+fn looks_like_quote(c: char) -> bool {
+    // list of homoglyphs generated using the following wikidata query:
+    // SELECT ?u WHERE {
+    //   wd:Q87495536 wdt:P2444+ ?c.
+    //   ?c wdt:P4213 ?u.
+    // }
+    match c {
+        '\u{2033}' | '\u{02BA}' | '\u{02DD}' | '\u{030B}' | '\u{030E}' | '\u{05F4}'
+        | '\u{201C}' | '\u{201D}' => true,
+        _ => false,
+    }
+}
diff --git a/tests/ui/unicode-quote.rs b/tests/ui/unicode-quote.rs
new file mode 100644
index 0000000000000..0421fdb85041d
--- /dev/null
+++ b/tests/ui/unicode-quote.rs
@@ -0,0 +1,3 @@
+fn main() {
+    dbg!("since when is \“THIS\” not allowed in a string literal");
+}
diff --git a/tests/ui/unicode-quote.stderr b/tests/ui/unicode-quote.stderr
new file mode 100644
index 0000000000000..f418bbb65fa2e
--- /dev/null
+++ b/tests/ui/unicode-quote.stderr
@@ -0,0 +1,20 @@
+error: unknown character escape: `\u{201c}`
+  --> $DIR/unicode-quote.rs:2:26
+   |
+LL |     dbg!("since when is \“THIS\” not allowed in a string literal");
+   |                          ^ unknown character escape
+   |
+   = help: \u{201c} is not an ascii quote, but may look like one in some fonts.
+           consider writing it in its escaped form for clarity.
+
+error: unknown character escape: `\u{201d}`
+  --> $DIR/unicode-quote.rs:2:32
+   |
+LL |     dbg!("since when is \“THIS\” not allowed in a string literal");
+   |                                ^ unknown character escape
+   |
+   = help: \u{201d} is not an ascii quote, but may look like one in some fonts.
+           consider writing it in its escaped form for clarity.
+
+error: aborting due to 2 previous errors
+