Radagast is the Tolkien character known as a Maia who serves the Vala Yavanna.
Radagast is one of the five Istari, or Wizards, sent to Middle-earth in the Third Age to oppose Sauron. His mission is connected with the welfare of living things, and his close relationship with animals and birds reflects his association with Yavanna, the Vala of growing things. He is also called Radagast the Brown.
Unlike Gandalf and Saruman, Radagast plays a relatively small role in The Hobbit and The Lord of the Rings. He helps Gandalf indirectly by sending the bird Gwaihir and becomes part of the information surrounding Dol Guldur. His portrayal in later screen adaptations expands some aspects of his character.
Saruman and Gandalf are also Maiar, but they serve different narrative roles. Sauron is a Maia who became Morgoth’s chief servant, not an Istar sent as a protector of Middle-earth.