Is the word us first person second person or third person?

The pronoun "us" is the first person, plural, objective, the ones speaking.

The corresponding first person, plural, subjective pronoun is "we".

The first person, singular, subjective is "I"; the first person, singular, objective is "me."

The second person is "you" for both singular and plural, subjective and objective.

The third person is "he," "she," "it," or "they" subjective; "him," "her," "it," or "them" objective.