Book of Judith

The Book of Judith is part of the Bible. It was written in or near 100 b.c.e. It is in Bibles that follow the Catholic and Orthodox Canon. Protestants and Jews treat the Book of Judith as part of the apocrypha and not part of the official canon.
In the book, an evil general named Holofernes is invading Israel. He is waiting with his army outside the town of Bethulia and will not let the people in the town get any water to drink. Judith tells the people of Bethulia not to give up. She sneaks to Holofernes' camp and pretends to make friends with him. He invites her to a meal, where he drinks much alcohol. When he falls asleep, she cuts off his head.
History.
The Book of Judith is probably not a story about something that really happened. The book says that Holofernes was an Assyrian who worked for Nebuchadnezzar, but the real Nebuchadnezzar was a Babylonian ruler.
The book starts with, "In the twelfth year of the reign of Nebuchadnezzar, who reigned over the Assyrians in Nineveh." Many ancient Hebrew stories started with words like these. It is like saying "once upon a time": it tells the reader to expect a fairy tale.
In culture.
Many, many artists have painted paintings of Judith killing or preparing to kill Holofernes. For example, Artemisia Gentileschi and Gustav Klimt.