Adyar or Adayar may refer to:
- Adyar, Bhandara, a small town in Maharashtra, India
- Adyar, Chennai, a locality of Chennai, Tamil Nadu, India
- Battle of Adyar, October 1746
- Adyar River, a river in Chennai city
- Adyar Creek
- Adyar Eco Park (also known as Tholkappia Poonga), an ecological park set up in the Adyar estuary area
- Adyar Ananda Bhavan, Indian vegetarian restaurant chain
- Adyar Cancer Institute
- Adyar Film Institute
- Adyar Gate, another name of ITC Sheraton Park hotel & Towers in Chennai
- Adyar Kamakshi Temple
- Adyar Library
- Theosophical Society Adyar, an international occult organisation headquartered in Adyar, Chennai
- Adyar, Karnataka, a town in Karnataka, India
- Adayar (horse), an Irish-bred Thoroughbred racehorse
- Adyar K. Lakshman, Indian dancer and choreographer