No, UFC fighters are not allowed to bet on themselves. This is a standard practice across most combat sports and professional leagues to maintain the integrity of the competition. Betting on oneself could lead to potential conflicts of interest, manipulation of the outcome, or the appearance of match-fixing.
The UFC, as well as other major sports organizations, has strict policies against athletes betting on their own fights or on any fights within the organization. These policies are enforced to ensure fair competition and to protect the reputation of the sport. Violations of these policies can result in fines, suspensions, or even termination of contracts.