Mehmet Sait Halet Efendi (1761–1822) was an Ottoman diplomat and politician, ambassador to Paris from 1803 to 1806 and later the favourite and Inner Minister of the sultan Mahmud II. He was ambassador to the court of Napoleon I until 1806, and was succeeded in this role by Muhib Efendi, who was ambassador from 1806 to 1811.
In 1819 Halet Efendi brought the attention of Sultan Mahmud II to the power-grabbing activities of Ali Pasha in Ottoman Europe. As Mahmud II sent an army against Ali Pasha, the latter responded by encouraging a rebellion against Ottoman power in Greece. These event led to the catastrophic Greek insurrection in 1821. Considered by the Sultan as contributing to the rebellion, Halet was banished from the court before being assassinated in Konya, present-day Turkey, in November 1822. He was strangled and beheaded.