Cynthia Nonyelum Sember (née Ofili; born 5 August 1994) is an American-born British track and field athlete, specialising in sprint hurdles.

[1][2] In 2014, her sophomore year at the University of Michigan, Ofili qualified for the 60 m hurdles final at the NCAA indoor championships, placing sixth in a personal best 8.07; outdoors, she broke 13 seconds in the 100 m hurdles for the first time, winning the Big Ten conference championship in 12.93.

[4] Ofili's times improved in 2015, and she became a leading collegiate hurdler;[5] at the NCAA outdoor championships in Eugene she placed second in a personal best 12.60, losing only to Keni Harrison of Kentucky.

[6] She also qualified for the NCAA championship meet in the flat 100 m, but despite running a school record 11.39 she was eliminated in the semi-finals in that event.

After winning the 100 metres hurdles gold medal at the 2024 British Athletics Championships, Sember was subsequently named in the Great Britain team for the 2024 Summer Olympics.