Apple’s now-CEO Tim Cook offered part of his liver to his legendary boss, Steve Jobs, two years before the tech guru died of cancer, according a new Jobs biography.

Jobs was in desperate need of a liver transplant in 2009 when Cook learned he had the same rare blood type as Jobs and was also able to grow back lost liver cells, according to ­the book, “Becoming Steve Jobs.”

“I said, ‘Steve, I’m perfectly healthy,’ ” Cook says in the book, according to an excerpt posted by Fast Company. “ ‘I can do this and I’m not putting myself at risk; I’ll be fine.’ ”

But Jobs declined the ­offer from his eventual successor.