LAS VEGAS — Conor McGregor made his triumphant return to the Octagon with a first-round TKO over Donald Cerrone. The energy was palpable as the Irishman finished “Cowboy” in the first minute of their welterweight bout, then used his post-fight interview to call out the rest of the division.

In the co-main event, Holly Holm once again defeated Raquel Pennington in a rematch of their closely contested bout in February of 2015.

UFC 246 main card results

Conor McGregor (23-4) def. Donald Cerrone (36-15) via TKO (punches) at 0:40 of R1

• Round 1: McGregor comes out and swings and misses. Seconds later it was the beginning of the end as McGregor catches Cerrone with a kick to the head that drops “Cowboy.” Referee Herb Dean allowed Cerrone some time to recover while McGregor pounded him on the ground until Dean eventually stopped the fight.

Holly Holm (13-5) def. Raquel Pennington (10-9) via unanimous decision (29-28, 30-27 x 2)

Aleksei Oleinik (58-12-1) def. Maurice Greene (8-5) via submission (armbar) at 4:38 of R2

Brian Kelleher (20-10) def. Ode Osbourne (7-3) via submission (guillotine) at 2:49 of R1

Diego Ferreira (17-2) def. Anthony Pettis (22-10) via submission (rear-naked choke) at 1:46 of R2

UFC 246 prelims results

Roxanne Modafferi (24-15) def. Maycee Barber (7-1) via unanimous decision (30-27 x 2, 30-26)

Sodiq Yusuff (10-1) def. Andre Fili (19-7) via unanimous decision (29-28 x 3)

Askar Askarov (11-0) def. Tim Elliott (16-9-1) via unanimous decision (30-27 x 2, 29-28)

Drew Dober (21-9) def. Nasrat Haqparast (10-3) via TKO at 1:10 of R1

UFC 246 early prelims results

Aleksa Camur (6-0) def. Justin Ledet (9-3) via unanimous decision (30-27 x 2, 29-28)

Sabina Mazo (8-1) def. J.J. Aldrich (8-4) via split decision (29-28 x 2, 28-29)

More UFC 246 coverage from Yahoo Sports:

• Can Cerrone finally get a win on the big stage?

• McGregor tones down his act, once again seems likable

• Win or lose, plenty of options for McGregor’s next fight

• Viewer’s guide: How to watch McGregor vs. Cerrone