In enzymology, a thymidine-triphosphatase () is an enzyme that catalyzes the chemical reaction
Thus, the two substrates of this enzyme are dTTP and H<sub>2</sub>O, whereas its two products are dTDP and phosphate.
This enzyme belongs to the family of hydrolases, specifically those acting on acid anhydrides in phosphorus-containing anhydrides. The systematic name of this enzyme class is dTTP nucleotidohydrolase. Other names in common use include thymidine triphosphate nucleotidohydrolase, dTTPase, and deoxythymidine-5'-triphosphatase. This enzyme participates in pyrimidine metabolism.