红细胞生成（英语：erythropoiesis）是指红细胞的生成过程。

缺氧时，会促进肾脏产生促红细胞生成素。这种激素可以刺激红细胞前体细胞的增殖分化，并最终在造血组织中发育成为成熟的红细胞。对出生后的鸟类与哺乳动物（包括人类）来说，红骨髓是生成红细胞的器官。而在胚胎初期，红细胞在卵黄囊的中胚层细胞中形成。当到3或4个月时，脾、肝负责生成红细胞。7个月之后，骨髓开始生成红细胞。在罹患某些疾病的人以及某些动物中，也会出现脾、肝生成红细胞的情形，被称为髓外红细胞生成（extramedullary erythropoiesis）。

Erythropoiesis (from Greek 'erythro' meaning "red" and 'poiesis' meaning "to make") is the process which produces red blood cells (erythrocytes). It is stimulated by decreased O₂ in circulation, which is detected by the kidneys, which then secrete the hormone erythropoietin. This hormone stimulates proliferation and differentiation of red cell precursors, which activates increased erythropoiesis in the hemopoietic tissues, ultimately producing red blood cells. In postnatal birds and mammals (including humans), this usually occurs within the red bone marrow. In the early fetus, erythropoiesis takes place in the mesodermal cells of the yolk sac. By the third or fourth month, erythropoiesis moves to the liver. After seven months, erythropoiesis occurs in the bone marrow. Increased level of physical activity can cause an increase in erythropoiesis. However, in humans with certain diseases and in some animals, erythropoiesis also occurs outside the bone marrow, within the spleen or liver. This is termed extramedullary erythropoiesis.