Zephaniah lived about 2600 years ago. He might have been a great grandson of king Hezekiah (Zephaniah 1:1). If so, then Zephaniah would have been a cousin of King Josiah, during whose reign he prophesied.
Zephaniah was a prophet to Judah (the southern part of the Jewish homeland, which includes Jerusalem), during the year before its destruction by the Babylonians in 586 BC. Zephaniah was stern and austere, much like the prophet Amos. He announces the doom of idol worshipers, greedy people, treacherous merchants, faithless prophets, and some of the surrounding nations. The message of Zephaniah was a strong affirmation of the first commandment "You shall have no other gods besides Me".
The Bible's book of Zephaniah deals mainly with the Day of Judgment. He also predicted Nineveh, the capitol of Assyria, would become a deserted ruin (which it is, today, despite the fact that it was in Zephaniah's time the capital of the Assyrian Empire). Zephaniah's ministry followed Isaiah's ministry by about 75 years.
Zephaniah means "The Lord has hidden away". His book is the ninth book of the Minor Prophets.