Histone-arginine N-methyltransferase (, histone protein methylase I, nuclear protein (histone) N-methyltransferase, protein methylase I, S-adenosyl-L-methionine:histone-arginine omega-N-methyltransferase) is an enzyme with systematic name S-adenosyl-L-methionine:histone-arginine Nomega-methyltransferase. This enzyme catalyses the following chemical reaction
The enzyme forms the Nomega-monomethyl- and Nomega,Nomega'-dimethyl.