In enzymology, a ribose-5-phosphate adenylyltransferase () is an enzyme that catalyzes the chemical reaction
Thus, the two substrates of this enzyme are ADP and D-ribose 5-phosphate, whereas its two products are phosphate and ADP-ribose.
This enzyme belongs to the family of transferases, specifically ones transferring phosphorus-containing nucleotide groups (nucleotidyltransferases). The systematic name of this enzyme class is ADP:D-ribose-5-phosphate adenylyltransferase. Other names in common use include ADP ribose phosphorylase, and adenosine diphosphoribose phosphorylase.