The women's 800 metres at the 2008 Summer Olympics took place on 15–18 August at the Beijing National Stadium.

Marilyn Chinwenwa Okoro is a British track and field athlete. She finished third in the 800 metres at both the 2007 and 2008 IAAF World Athletics Final. She was on the bronze winning 4 × 400 m relay at the 2007 World Championships in Athletics. She represented Great Britain at the Beijing Olympic Games in 2008 and finished sixth (1:59.53 mins) in the semi-finals. She was part of the 4 × 400 m relay team which finished fifth in the final of the 2008 Summer Olympics although the team was later upgraded to bronze medal position following disqualification for doping offences of the teams finishing in third and fourth place.