Targum Jonathan (תרגום יונתן בן עוזיאל), otherwise referred to as Targum Yonasan/Yonatan, is the official eastern (Babylonian) targum to the Nevi'im. Its early origins, however, are western (i.e. from the Land of Israel), and the Talmudic tradition attributes its authorship to Jonathan ben Uzziel, a pupil of Hillel, a doctor of the Law at Jerusalem in the time of King Herod. Its overall style is very similar to that of Targum Onkelos, though at times it seems to be a looser paraphrase.
The language of Targum Jonathan is Aramaic.
In Talmudic times (and to this day in Yemenite Jewish communities) Targum Jonathan was read as a verse-by-verse translation alternatively with the Hebrew verses of the haftarah in the synagogue. Thus, when the Talmud states that "a person should complete his portions of scripture along with the community, reading the scripture twice and the targum once" (Berakhot 8a-b), the passage may be taken to refer to Targum Jonathan (as well as to Targum Onkelos on the Torah).