Gregory Kelly (March 16, 1892 – July 9, 1927) was an American stage actor, who began performing as a child. He was a Broadway attraction, starring in such long-running productions as Seventeen and The Butter and Egg Man. His early death precluded him from appearing in more than two films. He is remembered today as the first husband of Ruth Gordon, who credited him with teaching her acting.

Gregory Kelly was born on March 16, 1892, in New York City, to Thomas J. Kelly, a letter carrier, and his wife Agnes J. Kelly. His grandparents on both sides were immigrants to New York from Ireland. He was the youngest of three sons; his older brother Thomas J. Kelly Jr. would also become an actor. When he was two, he had rheumatic fever, which Ruth Gordon later speculated may have damaged his heart.

Actress Grace Menken recalled that as a child Gregory Kelly went through Anna Taliaferro's theatrical agency with her and her sister Helen Menken. Kelly's first verifiable stage credit came in January 1904 with a production of The Light That Lies in Woman's Eyes. He and his older brother Tommy were jointly billed as "Two Boys, sons of Red Head". The play starred Virginia Harned, whose then husband E. H. Sothern had written it for her. When the production went on tour in February, the Kelly brothers went with it.

Kelly next appeared in a touring production of After Midnight, starting in September 1904, in which he received his first critical notice: "Master Gregory Kelly... also comes in for a large share of the applause". This tour lasted through the end of February 1905, resumed in September 1905 with new producers and a new leading man, and finished up in February 1906.

During 1908 Kelly joined a touring vaudeville musical called School Days by Gus Edwards, who also produced. It played Broadway for a month starting in September 1908, resuming touring in late October. He stayed with this tour through April 1909.

The quality of plays he appeared in, and Kelly's professional skills, improved after he joined "The Manhattan Company" of Mrs. Fiske in 1910. He later attributed to her tutoring his success in stage acting, particularly in timing dialogue pause and response. Harrison Grey Fiske first cast Kelly as a thirteen-year-old boy in a revival of Ibsen's The Pillars of Society. The production would have a three-day tryout in Rochester, New York, followed by a two-week engagement on Broadway. The play was accorded only mild interest by the New-York Tribune reviewer, but they commended the acting of the entire company. Kelly "...spoke with understanding and carried himself modestly, disdaining the 'smartness' which is the usual fault of stage boys." Following Pillars, Kelly then spent two weeks in a more adult role for a one-act curtain-raiser to Mrs. Fiske's main feature, Hannele.

The Fiskes took their production of Pillars on tour across the country, Kelly accompanying. While on the road, the Fiskes tried out a revival of Langdon Mitchell's Becky Sharp, a dramatization of Vanity Fair. Mrs. Fiske had been the original producer and director of this 1899 work. Kelly played a minor role in Becky Sharp, so the Fiskes made him assistant stage manager. Kelly was still with the Fiskes when Becky Sharp finished a two-week engagement on Broadway in early April 1911.

By late November 1911, Kelly was reported to have joined the cast of Klaw and Erlanger's Kismet, to be directed by Harrison Grey Fiske. This spectacular production had its US premiere at the Knickerbocker Theatre on December 25, 1911. The cast was so large that it was divided into three sections in newspapers for just the principals.