Banaili Raj also known as Garhbanaili Raj was a zamindari estate based in the Indian state of Bihar. They were considered one of the ruling dynasties of the Mithila region.Rulers and holders of this estate were Maithil Brahmin. The name of the estate derives from a village Banaili in the then Purnia district of Bihar. The main centres of residences of Rajas of Banaili are Banaili, Ramnagar, Champanagar, Srinagar, Garh Banaili, and Sultanganj. Bhagalpur was the centre from where administration of the estate was carried out.