Ḫāʾ (خ, transliterated as ḫ (DIN-31635), ẖ (ISO 233), "kh" or "x"), is one of the six letters the Arabic alphabet added to the twenty-two inherited from the Phoenician alphabet (the others being ṯāʼ, ḏāl, ḍād, ẓāʼ, ġayn). It is based on the ḥāʾ  ح. It represents the sound [x] or [χ] in Modern Standard Arabic. The pronunciation of خ is very similar to German, Scottish, and Polish unpalatalised "ch", Russian х (Cyrillic Kha), and Spanish "j". In name and shape, it is a variant of ḥāʾ. South Semitic also kept the phoneme separate, and it appears as South Arabian , Ge'ez Ḫarm ኀ. Its numerical value is 600 (see Abjad numerals).

The most common transliteration in English is "kh", e.g. Khartoum (الخرطوم al-Kharṭūm), sheikh (شيخ).

Ḫāʾ is written is several ways depending in its position in the word: