The gayal (Bos frontalis), also known as mithun or Drung ox, is a large semi-domesticated cattle in the Himalayan foothills of South and primarily in Northeast India.

In his first description of 1804, Aylmer Bourke Lambert applied the binomial Bos frontalis to a domestic specimen probably from Chittagong.

In 2003, the International Commission on Zoological Nomenclature fixed the first available specific name based on a wild population that the name for this wild species is valid by virtue of its being antedated by a name based on a domestic form. Most authors have adopted the binomial Bos frontalis for the domestic species as valid for the taxon.

Phylogenetic analysis corroborates the taxonomic assessment that the gayal is an independent Bos species originating matrilineally from gaur, zebu and taurine cattle.

There are two major hypotheses on the origin of the gayal:

Analysis of the genome of the gayal was published in 2017. In 2020, a phylogenetic analysis using complete mitochondrial genome sequences unambiguously indicated that the gaur is the maternal ancestor of domestic mithun. It was probably domesticated over 8,000 years ago along the Assam-Burma border, with wild gaur the most likely ancestor along with some gene introgression from zebu, Southern yellow cattle, and cattle.

The gayal differs in several important particulars from the gaur:

Some domesticated gayals are parti-coloured, while others are completely white.^{[citation needed]}