Isabel Emily Jay (17 October 1879 – 26 February 1927) was an English opera singer and actress, best known for her performances in soprano roles of the Savoy Operas with the D'Oyly Carte Opera Company and in Edwardian musical comedies. During Jay's career, picture postcards were immensely popular, and Jay was photographed for over 400 different postcards.
After studying at the Royal Academy of Music, Jay joined the D'Oyly Carte Opera Company in 1897, with whom she began singing principal roles immediately, becoming the company's leading soprano in 1899, where she played leading roles in comic operas including The Rose of Persia, The Pirates of Penzance, Patience, The Emerald Isle and Iolanthe. She married and left the company in 1902. She returned to the West End stage in 1903 and starred in eleven musicals over the ensuing years, including A Country Girl, The Cingalee, Véronique, The White Chrysanthemum, The Girl Behind the Counter, Miss Hook of Holland, King of Cadonia and The Balkan Princess. She retired in 1911 at age 31.
Jay's health began to deteriorate due to the effects of scarlet fever as a child, and she died at age 47 in Monte Carlo, having been on a cruise with her husband. In recognition of her achievements, the Royal Academy of Music two years later instituted the Isabel Jay Memorial Prize.