三磷酸鸟苷（英语：guanosine triphosphate, GTP）即是鸟嘌呤-5'-三磷酸。在生物化学的全名为9-β-D-呋喃核糖鸟嘌呤-5'-三磷酸，或者是9-β-D-呋喃核糖-2-氨基-6-氧-嘌呤-5'-三磷酸。GTP是DNA复制时的引物和转录（即是mRNA的生物合成）时的鸟嘌呤核苷酸的提供者。它是三羧酸循环中琥珀酸辅酶A转变为琥珀酸过程中的能量载体，它可以和ATP相互转换。

GTP也是细胞信号传导的重要物质，在此过程中它会在三磷酸鸟苷酸酶 (en:GTPase)作用下水解为GDP。

Guanosine-5'-triphosphate (GTP) is a purine nucleoside triphosphate. It can act as a substrate for the synthesis of RNA during the transcription process of DNA during DNA replication. Its structure is similar to that of the guanine nucleobase, the only difference being that nucleotides like GTP have a ribose sugar and three phosphates, with the nucleobase attached to the 1' and the triphosphate moiety attached to the 5' carbons of the ribose.