The 20-year old shot stopper has represented his country in each age group from the under 17 level through to under 20s.
Standing at 6ft 4ins tall, the Fleetwood-born keeper made his debut for The Fishermen in 2018 and spent the last two seasons on loan with FC United of Manchester and Chorley respectively.
Crellin, speaking to bwfc.co.uk, said: “The move came around pretty fast for me and as soon as I found out Bolton Wanderers were interested I couldn’t turn down a club of this magnitude.
“I want to come here, play and impress, and to help this club get back to where it belongs.
”At my age, playing at Bolton Wanderers in a stadium like this and with a great fan base behind us, it will be a brilliant opportunity for me to kick on.
“The way Ian plays football is right up my street and I cannot wait to play.”
Bolton Wanderers Head Coach Ian Evatt added: ”Billy has a fantastic pedigree, being an England U20 goalkeeper, and we are delighted that he has joined us on loan from Fleetwood.
“He is the modern day goalkeeper who is very agile, great with the ball at his feet and commands his area well.
“Billy comes to the club highly recommended.”
[You must be registered and logged in to see this link.]
[You must be registered and logged in to see this image.]