Final answer:
Erythropoietin is the hormone produced by the kidneys that stimulates the production of red blood cells (RBCs).
Step-by-step explanation:
The hormone that stimulates the production of red blood cells (RBCs) is called erythropoietin (EPO), and it is produced by the kidneys.
EPO is released in response to low levels of oxygen in the blood. It stimulates the bone marrow to produce more RBCs, increasing the level of oxygen carried in the blood.