Hemoglobin Theta -1 is a protein found in mammals, which acts as oxygen transporter in the blood. It is part of the hemoglobin tetramer which is produced in large quantities of red blood cells. Especially theta globin is formed in humans only during embryonic development. Theta -globin is one of the globins.

The theta- globin mRNA is to be found in the human fetal erythroid tissues, but not in erythroid or other non- erythroid tissues of adults. The theta- 1 genes expressed very early in embryonic life, sometimes perhaps even before the fifth week. Theta-1 is a member of the human alpha -globin gene cluster, which contains five functional genes and two pseudogenes. The order of the genes is: 5 ' - zeta - pseudo zeta - my - pseudo alpha-1 - alpha -2 - alpha -1 - theta1 - 3'. Research in favor of a transcriptionally active role for the gene and a functional role for peptides in specific cells, possibly in those of early erythroid tissue.