In the Bible, who took over Belshazzar's empire?

In the Bible, Darius the Mede took over Belshazzar’s empire after Belshazzar was killed.

The event is described in Daniel 5. During Belshazzar’s feast, a mysterious writing appears on the wall, and Daniel interprets it as a judgment against the Babylonian king. That same night, Belshazzar dies, and Daniel 5:31 says that Darius the Mede receives the kingdom at the age of 62.

This answer refers to the biblical account, not to a settled identification in modern ancient-history scholarship. The historical fall of Babylon occurred in 539 BCE, when the city was captured by forces associated with Cyrus the Great. Because of that, readers sometimes answer Cyrus instead. In the Book of Daniel, however, the immediate successor named after Belshazzar is Darius the Mede. His identity and relationship to Cyrus remain subjects of scholarly debate, but Darius is the canonical answer to this Bible-trivia question.