Who was the first latin to win an Oscar?

It's important to be careful with terminology. "Latin" usually refers to the language, not a specific ethnicity.

The first person of Latin American descent to win an Oscar was:

* Anthony Quinn, who won Best Supporting Actor for his role in "Viva Zapata!" in 1952.

It's worth noting that many other Latin American actors have gone on to win Oscars, but Quinn was the first.