UFC on Fox: Machida vs. Rockhold (also known as UFC on Fox 15) was a mixed martial arts event held on April 18, 2015, at the Prudential Center in Newark, New Jersey.

The event was the sixth event that the UFC has hosted in Newark, New Jersey and was headlined by a middleweight bout between former UFC Light Heavyweight champion Lyoto Machida and former Strikeforce Middleweight champion Luke Rockhold.

Manvel Gamburyan was expected to face Aljamain Sterling at the event. However, on February 3, Gamburyan pulled out of the bout citing injury and was replaced by Takeya Mizugaki.

A middleweight bout between Ronaldo Souza and Yoel Romero was originally booked for UFC 184. However, the bout was cancelled due to Souza being struck with pneumonia. The fight was later rescheduled for this event. However on April 10, Romero pulled out of the bout due to a ligament and meniscus tear in his knee. On the next day, Chris Camozzi was announced as his replacement. The fight was a rematch as Souza defeated Camozzi by technical submission (arm-triangle choke) at UFC on FX: Belfort vs. Rockhold.

A featherweight bout between Diego Brandão and Jimy Hettes was originally booked for UFC 183. However, the bout was canceled right before the event started, as Hettes passed out backstage. The fight was later rescheduled for this event.

George Sullivan was expected to face Kenny Robertson at the event. However, Robertson pulled out of the bout citing injury and was replaced by Tim Means.

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