Ada of Caria (Ἄδα in Greek) (fl. 377 – 326 BC) was satrap of Caria in the 4th century BC.
Ada was the daughter of Hecatomnus, satrap of Caria, and sister of Mausolus, Artemisia, Idrieus, and Pixodarus. She was married to her brother Idrieus, who succeeded Artemisia in 351 BC and died in 344 BC. On the death of her husband Ada became satrap of Caria, but was expelled by her brother Pixodarus in 340 BC; and on the death of the latter in 335 BC his son-in-law Orontobates received the satrapy of Caria from the Persian Great King.
When Alexander the Great entered Caria in 334 BC, Ada, who was in possession of the fortress of Alinda, surrendered the fortress to him. After taking Halicarnassus (modern Bodrum), Alexander committed the government of Caria to her; she, in turn, formally adopted Alexander as her son, ensuring that the rule of Caria passed unconditionally to him upon her eventual death.
According to Turkish archaeologists, the tomb of Ada has been discovered. Her remains are on display in the archaeological museum of Bodrum.