The 51st Lithuanian Infantry Regiment (Lithuanian: 51-ojo Lietuvos pėstininkų pulko; Russian: Литовский 51-й пехотный полк), known as the 51st Lithuanian Infantry Regiment of His Imperial Highness Heir to the Tsarevich (Russian: 51-й пехотный Литовский Его Императорского Высочества Наследника Цесаревича полк, romanized: 51-y pekhotnyy Litovskiy Yego Imperatorskogo Vysochestva Naslednika Tsesarevicha polk) from 1904, was an infantry regiment that served in the Imperial Russian Army.