Martina Pretelli was the sole representative of San Marino in athletics and was making her début at the Olympics at the age of 23. She was the first woman athletics competitor sent by San Marino to the Summer Olympics since the 1976 Montreal Games. Pretelli qualified by using a wild card because her best time of 12.15 seconds set at the 2011 Campionati Universitari Italiani in Turin was 0.77 seconds slower than the "B" qualifying standard for the women's 100 metres. San Marino was unable to send high jumper Eugenio Rossi because the governing body of athletics, the International Association of Athletics Federations, denied a request from the Sammarinese National Olympic Committee to allow him to compete in London. Pretelli was drawn in the fourth heat of the women's 100 metres on 3 August, finishing third out of nine runners with a time of 12.41 seconds. She placed 12th overall and did not advance into the quarter-finals after being two-tenths of a second slower than the slowest athlete who made the later stages. Afterwards, Pretelli revealed her training was delayed by tendinitis and she was only able to run three races going into the Olympics.