Valentinus can refer to:

• Pope Valentine
• Saint Valentine
• Basilius Valentinus, a 15th century monk from Erfurt who may have described bismuth
• Valentinius, a Gnostic also known as Valentinus
• Roman emperors - Valentinian I (364 - 375 CE) and Valentinian II (371 - 392)
• Valentinus a Roman exile who attempted a conspiracy in Roman Britain