In Exodus, what was the first plague sent against Egypt?

In Exodus, the first plague sent against Egypt was water turned to blood.

Aaron struck the Nile with Moses's staff, and Exodus says that the river's water became blood. The text extends the effect to canals, ponds, and stored water in vessels. Fish died, the river smelled, and the Egyptians had difficulty finding drinkable water.

This plague begins the sequence of judgments directed against Pharaoh and Egypt. It also directly affects the Nile, a river essential to Egyptian agriculture, transport, and settlement. Pharaoh's magicians imitate the sign, and Pharaoh's heart remains hardened according to the narrative.

The first plague is often confused with the final plague, the death of the firstborn, or with later plagues such as frogs and hail. The order in Exodus begins with the Nile's water becoming blood, followed by frogs, gnats or lice, flies, livestock disease, boils, hail, locusts, darkness, and finally the death of the firstborn.