Fetal hemoglobin, or foetal haemoglobin (also hemoglobin F, HbF, or α₂γ₂) is the main oxygen carrier protein in the human fetus. Hemoglobin F is found in fetal red blood cells, and is involved in transporting oxygen from the mother's bloodstream to organs and tissues in the fetus. It is produced at around 6 weeks of pregnancy and the levels remain high after birth until the baby is roughly 2–4 months old. Hemoglobin F has a different composition than adult forms of hemoglobin, allowing it to bind (or attach to) oxygen more strongly; this in turn enables the developing fetus to retrieve oxygen from the mother's bloodstream, which occurs through the placenta found in the mother's uterus.

In the newborn, levels of hemoglobin F gradually decrease and reach adult levels (less than 1% of total hemoglobin) usually within the first year, as adult forms of hemoglobin begin to be produced. Diseases such as beta thalassemias, which affect components of the adult hemoglobin, can delay this process, and cause hemoglobin F levels to be higher than normal. In sickle cell anemia, increasing the production of hemoglobin F has been used as a treatment to relieve some of the symptoms.