There was a collision between two comm satellites about 16 years back [1], and that was with satellites that we could track and theoretically control - with the debris collision of 2005 [2], that makes two events.

We've been lucky that this is the only publicly known satellite to collide with another satellite, other than satellites that got shot down as a demonstration of power.

[1] https://en.wikipedia.org/wiki/2009_satellite_collision

[2] https://www.space.com/969-china-space-debris-collide-orbit.h...

There is a Wikipedia page:

https://en.wikipedia.org/wiki/Satellite_collision