Lucius Seius Herennius Sallustius (died 227) was a Roman usurper in 227. He was a son of Seius (b. ca 155) and his wife Herennia Orbiana (b. ca 160), and paternal grandson of Publius Seius Fuscianus. Sallustius was father-in-law to Alexander Severus and was raised to the rank of Caesar probably when his daughter, Sallustia Orbiana, was wed to the emperor in 225. He made an attempt on the life of his son-in-law and as a result was executed two years later. His daughter was banished to Libya.