Here, Press Association Sport examines those in contention to be his next opponent.
1. The winner of Deontay Wilder v Tyson Fury
Wilder, the WBC champion, next defends his title against former unified champion Fury on December 1 at a US venue that will be confirmed in the coming week. The winner that evening will feel he has established himself as the world's leading heavyweight, as well as possessing the only title to so far elude Joshua.
Either against Joshua for all four world titles, to establish an undisputed champion, would become the most lucrative fight in the division.
2. The winner of Dillian Whyte v Dereck Chisora
Plans exist for a rematch between Whyte and Chisora to take place in London in December, two years after Whyte narrowly won on points in one of the fights of the year. Whyte, who defeated his bitter rival Joshua while both were amateurs, has improved significantly since then, as he most recently demonstrated by defeating Joseph Parker.
On that same July evening Chisora secured perhaps his finest win by stopping Carlos Takam. Whyte will be the favourite for if and when their rematch is made, and would prove a popular opponent having forced an entertaining fight when being knocked out by Joshua in December 2015.
3. Jarrell Miller
The undefeated American must first overcome Tomasz Adamek when they fight on October 6, but he was in contention to challenge Joshua over the summer and has since had a heated, public exchange with the champion. It is also in America where Matchroom hopes to further Joshua's reputation, so he would prove a logical opponent before the pursuit of a higher-profile fight.