Wilder vs. Joshua Could Happen This Year, Says Showtime Honcho

The heavyweight fight everyone wants to see -- Deontay Wilder vs. Anthony Joshua -- could happen in the next 6 months ... says the man in charge of broadcasting the event.

TMZ Sports spoke to Stephen Espinoza -- Showtime's president of sports and event programming -- who tell us the "ball is rolling" on making the fight happen in 2018.

"Things are moving. Discussions are happening," Espinoza tells us.

Wilder and Joshua have been calling each other out publicly for the last year -- with Wilder recently saying he'd even fly to England to fight Joshua on his home turf.

Both guys seem down to fight -- it's just a matter of locking up a deal.

Espinoza tell us the fight would be massive -- bigger than Canelo Alvarez vs. GGG -- and only rivaled by Mike Tyson vs. Lennox Lewis in 2002 and the superfights of the 1980s.