On Clemency is a two volume (incomplete) hortatory essay written in 55–56 CE by Seneca the Younger, a Roman Stoic philosopher, to the emperor Nero in the first five years of his reign. From Seneca's remarks, it would appear that it was written after Nero had turned eighteen, which would place it after the murder of his rival Britannicus in 55 AD. It may therefore have been written partly as an apology, perhaps as a means of assuring the Roman nobility that the murder would be the end, not the beginning of bloodshed.
The work survives in a fragmentary state. Of an original three books, only the first and the beginning of the second survive