Zerubbabel was the Persian-appointed governor of Yehud (post-exilic Judah), a province of the Persian Empire, in the early part of the reign of Darius I (from 522 BCE). He is assumed to have been born in Babylonia among the Judean exiles there; his name may derive from Akkadian zer babili meaning “seed of Babylon.”
While Ezra 5:16 credits a figure by the name of Sheshbazzar with beginning the rebuilding of the temple soon after the first Judeans moved from Babylon to Judah following the end of the exile in 539 BCE, Haggai 1 says that temple building had not yet begun during the first year of the reign of Darius in 522, and Zerubbabel was likely the figure who oversaw its reconstruction.
Blenkinsopp, Joseph. “Zerubbabel.” Pages 71-103 in David Remembered: Kingship and National Identity in Ancient Israel. Grand Rapids, MI; Cambridge, England: Eerdmans, 2013.
Extensive further information about Zerubbabel can be found at Wikipedia.