Resh (Arabic: look below) is the twentieth letter of many Semitic alphabets, including Phoenician, Aramaic, Hebrew ר and Arabic alphabet rāʾ ر. Its sound value is one of a number of rhotic consonants: usually [r] or [ɾ], but also [ʁ] or [ʀ] in Hebrew.

In most Semitic alphabets, the letter resh (and its equivalents) is quite similar to the letter dalet (and its equivalents). In the Syriac alphabet, the letters became so similar that now they are only distinguished by a dot: resh has a dot above the letter, and the otherwise identical dalet has a dot below the letter. In the Arabic alphabet, rāʼ has a longer tail than dāl. In the Aramaic and Hebrew square alphabet, resh is a rounded single stroke while dalet is a right-angle of two strokes. The similarity led to the variant spellings of the name Nebuchadnezzar and Nebuchadrezzar.

The Phoenician letter gave rise to the Greek Rho (Ρ), Etruscan r , Latin R, and Cyrillic Р.

The word resh is usually assumed to have come from a pictogram of a head, ultimately reflecting Proto-Semitic *raʾ(i)š-. The word's East Semitic cognate, riš, was one possible phonetic reading of the Sumerian cuneiform sign for "head" (SAG 𒊕, ) in Akkadian.