“Girls Gone Wild” founder Joe Francis is a dad again … he’s welcomed a baby girl named Juliet Aurelia Francis … TMZ has learned.

Sources with direct knowledge tell TMZ … the baby was born March 18 in Mexico City … with Joe using a European egg donor and a surrogate.

We’re told Joe went all in on genetics … even calling Juliet the “best baby” in his eyes and telling people she’s absolutely perfect.

And after his messy feud with ex Abbey Wilson … including past claims she kidnapped their twin daughters, Alexandria Claire and Athena Olivia, born via IVF in October 2014 … we’re told he’s not taking any chances and isn’t letting Juliet out of his sight.