Phosphoribosyl-N-formylglycineamide (or FormylGlycinAmideRibotide, FGAR) is a biochemical intermediate in the formation of purine nucleotides via inosine-5-monophosphate, and hence is a building block for DNA and RNA.

[1][2] The vitamins thiamine[3] and cobalamin[4] also contain fragments derived from FGAR.

[5] FGAR is formed when the enzyme phosphoribosylglycinamide formyltransferase adds a formyl group from 10-formyltetrahydrofolate to glycineamide ribonucleotide (GAR) in reaction EC 2.1.2.2:[6] The biosynthesis pathway next converts FGAR to an amidine by the action of phosphoribosylformylglycinamidine synthase (EC 6.3.5.3), transferring an amino group from glutamine and giving 5'-phosphoribosylformylglycinamidine (FGAM) in a reaction that also requires ATP:[6]