UFC 231: Holloway vs. Ortega was a mixed martial arts event produced by the Ultimate Fighting Championship held on December 8, 2018 at Scotiabank Arena in Toronto, Ontario, Canada.

[3] A UFC Featherweight Championship bout between Max Holloway and Brian Ortega served as the event headliner.

[9] A lightweight bout between Gilbert Burns and Olivier Aubin-Mercier was previously scheduled to take place in February 2018 at UFC on Fox: Emmett vs. Stephens.

[13] In turn, on September 13, it was reported that Júnior was forced to withdraw as a surgery is required to treat the injury that caused the first cancellation of this bout.

[19] However, on December 4, it was announced that Ronson was pulled from the bout after Ontario Athletics Commission officials deemed that he was too heavy to safely make the lightweight 156-pound limit.