According to the Old Testament, ten plagues struck Egypt before the Israelites’ Exodus.
The plagues appear in the Book of Exodus, chapters 7–12. They begin when Moses and Aaron demand that Pharaoh release the Israelites from forced labor. The events culminate in the death of the firstborn, after which Pharaoh allows the Israelites to leave.
The sequence traditionally includes water turned to blood, frogs, gnats, flies, diseased livestock, boils, hail, locusts, darkness, and the death of the firstborn. The final plague is associated with the origin story of Passover.
A common mix-up is confusing the ten Egyptian plagues with the Ten Commandments, which are a separate set of laws presented later in Exodus. The Old Testament does not describe the plagues as occurring all at once; they are presented as a succession of signs and judgments.