A Founder­Prenup is an writ­ten le­gal agree­ment be­tween two or more part­ners that out­lines things like un­der what con­di­tions the com­pa­ny will run, what will hap­pen mon­ey and stock-wise should the com­pa­ny merge, be sold, or go un­der com­plete­ly, and what is ex­pect­ed of both part­ners. It pre­vents both part­ners from try­ing to screw each oth­er over should the com­pa­ny get suc­cess­ful or go un­der.