Pseudoephedrine (/ˌsjuːdoʊ.ᵻˈfɛdrɪn/ or /ˌsjuːdoʊˈɛfᵻdriːn/; PSE) is a sympathomimetic drug of the phenethylamine and amphetamine chemical classes. It may be used as a nasal/sinus decongestant, as a stimulant, or as a wakefulness-promoting agent.

The salts pseudoephedrine hydrochloride and pseudoephedrine sulfate are found in many over-the-counter preparations, either as a single ingredient or (more commonly) in combination with antihistamines, guaifenesin, dextromethorphan, and/or paracetamol (acetaminophen) or an NSAID (such as aspirin or ibuprofen).