Four pairs. I've never owned more than four.

Work - Black and can also be worn at formal occasions
Smart Casual - Grey ones. Hard to describe, they're just grey and white with laces
Casual - White adidas trainers
Running Shoes

They all pretty much falling apart, but I'm loathe to mass buy four pairs of new shoes since I'd probably have to go to at least four different stores to do so. I guess whichever ones literally fall off my feet first will be the first to be replaced.