The TV show Star Trek: Enterprise is canonically part of the Prime Universe, but some argue it belongs to both the Prime and Kelvin timelines.
The Kelvin Timeline was introduced in the 2009 Star Trek reboot movie, directed by J.J. Abrams and starring Chris Pine as James T. Kirk.
The movie replaced the original cast with new actors, but didn't follow a traditional reboot format.
Instead, it revealed that every other Star Trek TV show and movie remained part of the main canon, just in a different timeline.
Author's summary: Exploring Star Trek: Enterprise's timeline.