गाय हा एक सस्तन प्राणी असून भारताच्या पाळीव पशूंमधील अत्यंत महत्त्वाचा प्राणी आहे. प्राचीन काळापासून भारतात गाय ही प्रामुख्याने दूध, दही, ताक, लोणी इत्यादी दुग्धजन्य पदार्थांसाठी तसेच शेतीकरिता उपयुक्त पशुवंश पैदाशीसाठी पाळली जाते.

Cattle are large, domesticated, bovid ungulates widely kept as livestock. They are prominent modern members of the subfamily Bovinae and the most widespread species of the genus Bos. Mature female cattle are called cows and mature male cattle are bulls. Young female cattle are called heifers, young male cattle are oxen or bullocks, and castrated male cattle are known as steers.