I don't see any immediate age disqualifications. Off to the races!

Eye sight and fitness may be blockers, at least if your not a certain senator from Ohio.

I'm pretty sure the oldest astronaut (real astronaut, not billionaire who bought a 10min trip) is currently still going to space and is 65. Conveniently I couldn't find a source so I could also be making this up, but I'm 95% sure.