The 23 year old swept to glory in East London last summer, beating the reigning Olympic champion Roberto Cammarelle via count-back.
Joshua, who has signed a three year deal, joins fellow gold medallist Luke Campbell and Team GB captain Thomas Stalker into the Matchroom stable and will be trained by Tony Sims.
He said: “This is just the beginning. It’s going to be a very, very tough road but I’m willing to make the sacrifices.
"I'm totally overwhelmed, but moving forward, I don't think I'll ever regret this decision.
“Eddie Hearn advised me to look at all the offers and, after going away and doing just that, Matchroom was most definitely the best platform for me. I’ve done a lot of research and you cannot fault what they’re doing with their fighters.”
Promoter Hearn said: “Finally, we’ve got a heavyweight we can get very excited about.
"British boxing is on a high at the moment and Anthony can be a perfect role model — he really has got it all."
Topping the undercard, Welsh wizard Lee Selby (16-1) will defend his British and Commonwealth featherweight title against Cromer's Ryan Walsh (16-0) after Matchroom won the purse bids.
Dagenham lightweight Kevin Mitchell (34-2) will also feature in a ten rounder.
Rob McCracken, Great Britain performance director, said: "Anthony is a very talented sportsman who has enjoyed a meteoric rise to become Olympic champion, less than four years after he first began boxing.
"Naturally, it is a disappointment for us that Anthony has decided his future lies away from the GB Boxing programme, but he departs with our very best regards and we wish him every success in his future career."
Joshua had stated a desire to win an amateur world title before turning professional, having lost to Azerbaijan fighter Magomedrasul Majidov in the final of the 2011 competition.
- Sports & Recreation