In enzymology, a pyridine N-methyltransferase (EC 2.1.1.87) is an enzyme that catalyzes the chemical reaction

S-adenosyl-L-methionine + pyridine ${\displaystyle \rightleftharpoons }$ S-adenosyl-L-homocysteine + N-methylpyridinium

Thus, the two substrates of this enzyme are S-adenosyl methionine and pyridine, whereas its two products are S-adenosylhomocysteine and N-methylpyridinium.

This enzyme belongs to the family of transferases, specifically those transferring one-carbon group methyltransferases. The systematic name of this enzyme class is S-adenosyl-L-methionine:pyridine N-methyltransferase. This enzyme is also called pyridine methyltransferase.