Ringer's lactate solution, or lactated Ringer's solution, is a type of isotonic, crystalloid fluid further classified as a balanced or buffered solution used for fluid replacement.

The contents of Ringer's lactate include sodium, chloride, potassium, calcium, and lactate in the form of sodium lactate, mixed into a solution with an osmolarity of 273 mOsm/L and pH of about 6.5. In comparison, normal saline (NS) has an osmolarity of about 286 mOsm/L.

Ringer's lactate is largely used in aggressive volume resuscitation from blood loss or burn injuries