异喹啉（Isoquinoline）即苯并吡啶，是由萘中的一个 β-CH 基团被氮替换衍生出来的杂环化合物，与喹啉互为同分异构体，有芳香性。

异喹啉是无色低熔点片状结晶、固体或液体，有类似茴香油和苯甲醛混合物的香味，通常存放后颜色会发黄。存在于煤焦油和骨油中。微溶于水，溶于稀酸，能与多种有机溶剂混溶。能随水蒸气蒸发。具吸水性。有碱性，pK_a = 5.4，碱性较喹啉强，比吡啶略强，能与各种酸成盐，其盐酸盐熔点 209°C。

Isoquinoline is a heterocyclic aromatic organic compound. It is a structural isomer of quinoline. Isoquinoline and quinoline are benzopyridines, which are composed of a benzene ring fused to a pyridine ring. In a broader sense, the term isoquinoline is used to make reference to isoquinoline derivatives. 1-Benzylisoquinoline is the structural backbone in naturally occurring alkaloids including papaverine. The isoquinoline ring in these natural compound derives from the aromatic amino acid tyrosine.