The bayan (Russian: баян) is a type of chromatic button accordion developed in Russia in the early 20th century and named after the 11th-century bard Boyan.

The bayan differs from western chromatic button accordions in some details of construction:

The differences in internal construction give the bayan a different tone color from Western instruments, and the bass has a much fuller sound. Because of their range and purity of tone, bayans are often the instrument of choice for accordion virtuosi who perform classical and contemporary classical music. Two Soviet composers of note who wrote compositions for bayan are Vladislav Zolotaryov and Sofia Gubaidulina. Russian Bayan virtuoso Stas Venglevski has premiered contemporary works by Yehuda Yannay, Anthony Galla-Rini and William Susman.

Bayan may have the following meanings coming from various cultures

The word bayan (Mongolian: Баян, rich) is a common part of geographic names in both Mongolia and Inner Mongolia: