The woman withdrew her pension from the Post Office in the Weston Favell centre on Thursday, September 17.
As she left the shopping centre at about 1pm, a man ran past her and grabbed her handbag from her shoulder, causing her to fall to the floor.
Fortunately, the woman only suffered minor injuries, but she was left shaken by the robbery.
The bag which was stolen was beige, looked like it was made from leather and had a shoulder strap.
After taking the bag, the man ran away from the area of the bus stops.
Witnesses, or anyone who knows anything about this incident, can call Northamptonshire Police on 101.
Alternatively, they can call the independent charity Crimestoppers anonymously on 0800 555 111 or use the anonymous online form at www.crimestoppers-uk.org.