Which monkey god is a loyal devotee of Rama?

The monkey god who is a loyal devotee of Rama is Hanuman.

Hanuman is a divine vanara, or monkey-like heroic being, and one of the Ramayana’s most important allies of Rama. He represents the ideal combination of bhakti, or loving devotion, and shakti, or strength and courageous action. His loyalty is directed specifically toward Rama, whom he serves without seeking personal reward.

Hanuman first becomes central to Rama’s search for Sita after meeting Rama and Lakshmana in the forest. He helps form an alliance with Sugriva, the exiled vanara king, and then leaps across the ocean to Lanka. There he locates Sita in the Ashoka Vatika and gives her Rama’s message.

During the war, Hanuman performs extraordinary feats, including carrying the mountain bearing the life-restoring herb Sanjivani to save Lakshmana. In many later devotional traditions, he is worshipped as a powerful deity in his own right and as an exemplar of humility and service.

Sugriva is Rama’s vanara ally and king, Vali is Sugriva’s brother and rival, and Jambavan is a wise bear-like elder. All assist the story, but Hanuman is the famed devotee.