Poison Drummer Rikki Rockett -- Every Divoooorce Has Its PRENUP!!!

Rikki Rockett knows his prenup like he knows a power ballad.

The Poison drummer, represented by Mark Gross, just filed for divorce from Melanie Rockett, his wife of nearly 7 years -- and, according to the docs he wants to make sure they stick to the prenup she signed. Meaning ... not a cent more in spousal support than the agreed upon amount.

The Rocketts have 2 kids together – a 2 and 6-year-old – and Rikki wants joint custody.

Lighters up, and ... eeeevery cowboy sings a sad, sad song...