苯丙氨酸氨裂合酶（英语：phenylalanine ammonia-lyase，或称为苯丙氨酸解氨酶，简称为PAL，EC4.3.1.24）是一种催化如下化学反应的酶：

因此，这种反应有一种底物L-苯丙氨酸，以及两种产物反式-肉桂酸和氨。

这种酶属于裂合酶，而且是解氨酶，专门分解C-N键。此酶的系统命名为“L-phenylalanine ammonia-lyase (trans-cinnamate-forming)”。其他的英文俗名包括tyrase, phenylalanine deaminase、tyrosine ammonia-lyase、L-tyrosine ammonia-lyase、phenylalanine ammonium-lyase以及L-phenylalanine ammonia-lyase。这种酶会参与5个代谢途径：酪氨酸代谢、苯丙氨酸代谢、氮代谢、苯丙素苷生物合成以及生物碱生物合成ii。

Phenylalanine ammonia lyase (EC4.3.1.24) is an enzyme that catalyzes a reaction converting L-phenylalanine to ammonia and trans-cinnamic acid. Phenylalanine ammonia lyase (PAL) is the first and committed step in the phenyl propanoid pathway and is therefore involved in the biosynthesis of the polyphenol compounds such as flavonoids, phenylpropanoids, and lignin in plants. Phenylalanine ammonia lyase is found widely in plants, as well as some yeast and fungi, with isoenzymes existing within many different species. It has a molecular mass in the range of 270-330 kDa. The activity of PAL is induced dramatically in response to various stimuli such as tissue wounding, pathogenic attack, light, low temperatures, and hormones. PAL has recently been studied for possible therapeutic benefits in humans afflicted with phenylketonuria. It has also been used in the generation of L-phenylalanine as precursor of the sweetener aspartame.