4-Methylphenylpiperazine (also known as 1-(4-Methylphenyl)piperazine, 1-(p-Tolyl)piperazine, 254-534-6, 1-p-Tolyl-piperazine, 1-(4-methylphenyl)-piperazine, 4-methylphenyl piperazine, 4-(4-methylphenyl)piperazine, 1-(4-methyl-phenyl)-piperazine, STL169113 or CS-W017398) is a stimulant substance of the phenylpiperazine class.