The prime minister delivered her well-timed zinger after Corbyn tried to link the visit of Saudi Arabia's Mohammed bin Salman to International Women's Day.
"Tomorrow is International Women's Day," Corbyn started, "a chance to celebrate how far we've come ... but also reflect on how far we have to go."
He continued, "As she makes her arms sales pitch, will she also call on the crown prince to halt the shocking abuse of human rights in Saudi Arabia?"
"First of all," May responded, "I want to thank the right honorable gentleman for telling me it was International Women's Day tomorrow."
The chamber howled.
"I think that's what's called mansplaining," she said, receiving rousing applause and loud boos.
"I welcome the fact that the crown prince will be sitting with, and as of the guest, of a female prime minister," she said.