Riyadh in Saudi Arabia and Italian capital Rome have submitted bids to host the World Equestrian Games (WEG) and International Equestrian Federation (FEI) World Championships in eight disciplines in 2022.
The FEI confirmed 10 countries had submitted formal bids for the events.
The sport's worldwide governing body had previously revealed 20 nations had submitted an expression of interest to host one or more of the competitions.
This is the third round of bidding for these 2022 World Championships that the FEI has launched, although the first two were for the World Equestrian Games (WEG).
They had previously not received any realistic bids so the FEI Board last November decided to reopen the bid process for individual World Championships in all disciplines for 2022, with preference being given to multi-discipline bids.
Lexington in the United States and Šamorín in Slovakia had originally bid for the WEG before eventually withdrawing.
Since 1990, the FEI held individual World Championships but then eight of the Federation's 10 disciplines were brought together in the WEG.
Riyadh and Rome have both entered the race for the 2022 WEG as well as eight World Championships in jumping, endurance, driving, dressage, Para dressage, eventing, reining and vaulting.
Denmark, Estonia, Hungary, Ireland, Italy, Kingdom of Saudi Arabia, Slovakia, the Netherlands, United Arab Emirates and the United States of America have submitted a bid for at least one World Championships.
Herning in Denmark has entered the race for a combined jumping, dressage and Para dressage event.
Arizona in the United States wants to stage a joint reining and vaulting World Championships, while Millstreet in Ireland has bid for the eventing competition.
"The number of formal bids that we’ve received for single and multi-discipline FEI World Championships and full Games is an excellent indication that interest in the World Championships is as strong if not stronger than ever," FEI President Ingmar De Vos said.
“We knew that some of the countries that put in expressions of interest back in February were just dipping their toes in the water, but these formal bids are a great validation of the new bidding process and show that we have a really strong product.”