What is the Greek language equivalent of name James?

There isn't a direct, single Greek equivalent of the name James. James comes from the Hebrew name יעקב (Ya'akov), meaning "he who supplants" or "supplanter." The Greek translation of that Hebrew name is Ἰάκωβος (Iákōbos). This is the name used in the Greek Septuagint (the Greek translation of the Hebrew Bible). So, while not a direct *equivalent* in meaning, it's the closest and most historically accurate Greek rendering of the name.