What is the opposite of a mentiroso in spanish?

The opposite of a "mentiroso" (liar) in Spanish is "honesto" (honest) or "veraz" (truthful).

Here are some examples:

* "Él es un mentiroso." (He is a liar.)

* "Ella es una persona honesta." (She is an honest person.)

* "Su testimonio fue veraz." (His testimony was truthful.)