Plenty of examples to think about, but I suppose it depends on your definitions of really big: 1. Atlassian became very large before raising money, Github too

Plenty of examples to think about, but I suppose it depends on your definitions of really big: 1. Atlassian became very large before raising money, Github too 2. Litmus is a pretty large company, but not Billion dollar club (which is the typical "really big" moniker 3. Dyn was pretty huge $50M/year+ before they raised money