Gerda Gottlieb Wegener Porta (15 March 1886 - 28 July 1940) was a Danish illustrator and painter.

Originally from the provinces and the daughter of a clergyman, she moved to Copenhagen to pursue her education at the Royal Art Academy, and married fellow artist Einar Wegener (1882-1931) in 1904. After moving to Paris in 1912, she found much success both as a painter and illustrating for Vogue, La Vie Parisienne, Fantasio, and many other magazines. As she found fame in Paris, Gerda also developed a following in her home country. She held exhibitions at Ole Haslunds gallery in Copenhagen at regular intervals. Her career relied on a phenomenal talent but perhaps even more so on her notorious diligence, and the advantages her unusual marriage brought her.

Einar Wegener, who by many at the time was considered a more talented artist, toned down his own work and profile to help his wife in her artistic endeavors. In a female guise, "Lili", he became Gerda's favorite model. Einar Wegener eventually came out as a transsexual woman, and had the first publicly known sex reassignment surgery, in 1930, taking the name Lili Elbe. Gerda Wegener supported Elbe throughout her transition. The king of Denmark declared the Wegeners' marriage null and void in October 1930.

In 1931, Gerda Wegener married Major Fernando Porta (born 1896), an Italian officer, aviator, and diplomat, and moved with him to Morocco, specifically Marrakech and Casablanca. She divorced Porta in 1936 and returned to Denmark in 1938. She held her last exhibition in 1939, but by this time she was largely out of fashion.