Gemma Mengual Civil (born 12 April 1977 in Barcelona, Catalonia, Spain) is a Spanish synchronised swimmer. She has competed at the 2000, 2004 and 2008 Summer Olympics. On 15 February 2012 she announced her retirement. After retiring she became involved with coaching the national synchronised swimming team. However in June 2015 Mengual announced that she would return to competition with the aim of competing at the 2015 World Aquatics Championships in Kazan, Russia, in the mixed duet with Pau Ribas, whom she had previously coached. Although she had previously indicated that she would not compete beyond the World Championships, in September of that year she confirmed via social media that she would compete in the duet in the 2016 Summer Olympics with Ona Carbonell.
During the 2020 Olympic Games (celebrated in 2021 due to COVID) she collaborated in the broadcast for the swimming-pool and floor events giving technical insight and expert opinion on the Olympian sport women.