The reigning women’s and men’s Boston Marathon champions, Hellen Obiri and Sisay Lemma, will return to the Hopkinton start line April 21.

Kenyan Hellen Obiri will pursue a third straight Boston Marathon title in April, the Boston Athletic Association said on Wednesday, while Ethiopian Sisay Lemma will defend his title in a speedy men's field.

Both of the Boston Marathon's defending wheelchair champions will return in April to race the 26.2 miles from Hopkinton to Copley Square in the 129th edition of the historic event. This year's Boston Marathon will mark the 50th anniversary of Bob Hall’s pioneering 1975 finish,