2C-T-4 or 2,5-dimethoxy-4-isopropylthiophenethylamine is a psychedelic phenethylamine of the 2C family. It was first synthesized by Alexander Shulgin, sometimes used as an entheogen.

2C-T-4 is the 2-carbon homologue of Aleph-4. The full chemical name is 2-4-(isopropylthio)-2,5-dimethoxyphenylethanamine. The drug has structural and pharmacodynamic properties similar to 2C-T-7 and 2C-T-9.

2C-T-4 is usually taken orally, and the dosage range is typically 8-20 mg.

2C-T-4 produces psychedelic and entheogenic effects that develop slowly and can last 8–16 hours. Some users have also reported dissociative properties uncharacteristic of other psychedelic phenethylamines. While all users experience virtually no effects for the first hour after ingestion, results vary drastically between individuals and range from hallucination and euphoria to intense sickness and anxiety. Shulgin devoted a chapter in the first part of PiHKAL to this compound, describing it as an intense "plus-four" psychedelic.

The mechanism that produces 2C-T-4’s hallucinogenic and entheogenic effects has not been specifically established, however it is most likely to result from action as a 5-HT_2A serotonin receptor agonist in the brain, a mechanism of action shared by all of the hallucinogenic tryptamines and phenethylamines for which the mechanism of action is known.