The rapper, 36, popped the question on his girlfriend’s 33rd birthday on Monday in front of their family and friends, reports E!
Not one to do things by halves, Kanye hired the entire AT&T Park baseball stadium in San Francisco as the backdrop for his big moment according the US news website.
He had been in Los Angeles earlier in the day at the Hollywood Film Awards to present director Steve McQueen with an award, but reportedly flew straight to the Bay city area to see the birthday girl as a surprise.
Kim was allegedly seen boarding a private jet that afternoon with her family in Los Angeles.
The news comes after Kanye told fans during his concert in Seattle on Saturday that he planned to marry the mother of his child ‘one day.’
The marriage will be Kim's third, and Kanye's first.
Kim – who has previously been married to music producer Damon Thomas and basketball player Kris Humphries – told a US magazine in February:
‘[Marriage] is something I know that we both want in our future, but I don't have this sense of urgency about it,’
‘I have this best friend who understands me and helps me through all my tough experiences, and vice versa, you know? It just feels like this is it for me.’
The couple welcomed their first child – daughter North West – in June. When Kanye introduced little ‘Nori’ to the world by showing a photo on Kris Jenner’s talk show, Kim’s mum asked him if it was love at first sight between the pair.
‘Oh yeah, definitely,’ answered Kim’s baby-daddy.