cofounder

or co-found·er

[ koh-foun-der ]
/ koʊˈfaʊn dər /
|

noun

a person who founds or establishes something with another.

Origin of cofounder

First recorded in 1595–1605; co- + founder1
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for co-founder