Is Amaya a first name or a last name?

Amaya is both: a family name in some places and a given name in others. It is mostly a family name in Colombia and Argentina.

How to address someone called Amaya

Spain. Amaya is used both ways: 29% of people from Spain with this name in our data carry it as a family name. Look at where it sits in the name and how the person signs.
United States. Amaya is used both ways: about 33,218 people had it as a surname in the 2010 census, and 28,406 babies born between 1950 and 2017 were given it as a first name. Look at where it sits in the name and how the person signs.
Colombia. Amaya is a family name, usually written last. Write Dear Mr. Amaya or Dear Ms. Amaya.
Argentina. Amaya is a family name, usually written last. Write Dear Mr. Amaya or Dear Ms. Amaya.

Not sure which part of a full name is which? Check the full name with the country where the person is based.

People recorded in Wikidata who carry Amaya as a family name or as a given name, by country of citizenship (106 in total).

Country	As family name	As given name	Family name share
Spain	9	22	29%
United States	11	4	73%
Colombia	14	0	100%
Argentina	10	0	100%
Mexico	7	0	100%
El Salvador	5	1	83%
Japan	5	0	100%
Venezuela	4	0	100%
Peru	3	0	100%

Wikidata covers notable people, so counts show how the name is used, not how many people carry it.

As a surname: about 33,218 people in the 2010 census, rank 1,057 among US surnames.
As a first name: 28,406 babies born between 1950 and 2017, 100% of them girls.

More on this naming tradition: How Spanish names work.