Madras Bashai (Tamil: மெட்ராஸ் பாஷை, lit. 'Madras Language') was the variety of the Tamil language spoken by native people in the city of Madras (officially known as Chennai today) in the Indian state of Tamil Nadu. It was sometimes considered a pidgin, as its vocabulary was heavily influenced by Hindustani, Indian English, Telugu, Malayalam, and Burmese; it is not mutually intelligible with any of those except for Tamil, to a certain extent.

Since the advent of urbanization of the city especially since the Indian Independence, due to large immigrations into the city from different parts of Tamil Nadu, the Madras Bashai variety has become closer to normalized standard spoken Tamil. Today, the transformed variety is majorly called as Chennai Tamil.

Madras Bashai evolved largely during the past three centuries. It grew in parallel with the growth of cosmopolitan Madras. After Madras Bashai became somewhat common in Madras, it became a source of satire for early Tamil films from the 1950s, in the form of puns and double entendres. Subsequent generations in Chennai identified with it and absorbed English constructs into the dialect, making it what it is today's Chennai Tamil.