Brenda Mersereau Helser (May 26, 1924 – March 26, 2001), later known by her married name Brenda Helser de Morelos, was an American former competition swimmer who graduated Stanford University, and won a gold medal in the women's 4×100-meter freestyle relay at the 1948 Summer Olympics in London.

At the Mulnomah Club Helser was coached by International Swimming Hall of Fame member Jack Cody.

[10][11] Helser worked as a model during her swimming career and had a small role in the short movie "Aquaqueens" in 1946, likely after her move to Los Angeles.

[12][13] Helser's swam the 4x100 freestyle relay as the third swimmer in the 1948 London Olympics with Marie Corridon, Hawaiin native Thelma Kalama, and anchor Ann Curtis, a swimming rival in National competition, particularly in the 100-yard event.

In an exciting Olympic finish, American Ann Curtis began to gain time and pass the swimmer from the Dutch team that was in second place.