Eleventh Doctor's regeneration

The Eleventh Doctor, having expended the 12-regeneration life cycle beginning with the First Doctor, was enabled to undergo what he called "regeneration number thirteen" into the Twelfth Doctor after being provided with additional regeneration energy by the Time Lords. (TV: The Time of the Doctor)

However, in a timeline viewed by the Doctor at an earlier date, the Doctor was seen to have finally died, with their TARDIS growing its exterior dimensions and acting as his grave. (TV: The Name of the Doctor)