Ernst Peterson Hay (7 July 1886 – 31 December 1955) was a New Zealand lawyer and judge who was the Mayor of Lower Hutt from 1947 to 1949.

He was educated at Lawrence District High School and later became an assistant solicitor at the Public Trust Office in 1910.

During World War II Hay acted as chairman of the Armed Forces Appeal Board at Wellington.

[1] His brother was Christchurch businessman and city councillor Sir James Hay.

[7] His wife Agnes, who was a benefactor and volunteer for the Red Cross and Women's Guild, died in 1959.