Alice Walker, from Derbyshire, scored a perfect 14 out of 14 in her specialist subject, the Peak District.
Ms Walker – who won by six points in the grand final – was cheered on by a performance from the Morris dancing troupe she belongs to during the show, which aired on BBC Two on Monday.
The now 67-year-old said it was a “shock” to win.
“I applied for Mastermind after watching the programme and thought about entering for many years, but never expected to win, and it was quite a shock when I did,” the retired IT consultant said.
