Gayle King is a swimsuit model at the ripe age of 69 -- because she's on the cover of Sports Illustrated ... and even as a senior, she's showing off her rockin' bod.
The CBS News anchor was among 4 women tapped to appear on different covers of an upcoming SI issue -- and she's kinda the odd woman out, since the others are veteran models in the biz ... including Chrissy Teigen, Hunter McGrady and Kate Upton.