Charlotte Mary Chapin (née Hosmer; 12 December 1902 – July 1970) was an American female tennis player who was ranked No.

[3] Hosmer Chapin participated in the 1927 Wightman Cup, the team tennis competition between the United States and Great Britain.

[5] She won the singles title at the Pacific Coast Championships in June 1923, defeating Avery Follett in a three-sets final.

[8] Hosmer Chapin won the singles title at the Illinois State Championships in July 1925 after a win in three sets in the final against 16-year old Helen Jacobs.

[9] At the Eastern Grass Court Championships she was the finalist at the first two editions, in 1927 and 1928, losing the final to Molla Bjurstedt Mallory and May Sutton Bundy respectively.