Does changing a creature's controller affect which player's graveyard it goes to when it dies?

When a permanent is put into a graveyard from the battlefield, it goes to its owner's graveyard, regardless of who controls it at the moment it dies. This is stated in CR 400.1 and reinforced by CR 306.2 (for graveyards belonging to each player) and CR 800.4i.

Ownership is established when the game begins (or when the card enters the game) and cannot be changed by spells or abilities. Control, on the other hand, can shift temporarily through effects like Act of Treason or Threaten. So even if your opponent steals your creature and it dies while under their control, the creature card still goes your graveyard because you own it.

This matters practically for cards that care about creatures dying 'under your control' versus cards that trigger on creatures being put into your graveyard. For example, a Reanimator player cannot steal an opponent's Griselbrand, let it die, and have it enter their own graveyard — it returns to the original owner's graveyard.

Concrete example: Your opponent casts Act of Treason to gain control of your Grave Titan and attacks. A blocker kills the Titan. Even though your opponent controlled it at the moment of death, Grave Titan is placed in your graveyard because you are its owner (CR 400.1, CR 110.2).