The Latics have been on Espinoza's trail since his outstanding performances for Honduras during the Olympic tournament last summer.
And now Roberto Martinez has finally got his man, the 26-year-old midfielder is eager to get going.
"It's taken a while to get all the paperwork done but now I can concentrate on fighting for my place," said Espinoza.
"I just want to say a big thank you to everyone at the club who have been working so hard to get everything through in time - and for the manager to have the belief in me.
"Now it's down to business."