Hanuman is the monkey king who fights for the god Rama in the great Indian epic the Ramayana. Hanuman was the son of Anjani, a heavenly nymph (apsara) who had been cursed to take form as a monkey-person (varana) until such time as she gave birth to an incarnation of Shiva. When she was meditating one day, the god of the wind, Vayu, placed some sacred food in her hands. When she ate the food, she became pregnant with Hanuman and thus was freed from her curse. Because Vayu brought Anjani the blessed food, Hanuman was often called "Son of the Wind."
Hanuman's characteristics are bravery, strength, and devotion to God. He recognizes the divinity of King Rama and Queen Sita, themselves manifestations of Vishnu and Lakshmi, and he follows them to the ends of the earth. When Sita is stolen from her husband by the demon Ravana, Hanuman leaps across the whole ocean to save her.
Here's a description from William Buck's poetic retelling of the Ramayana:
"It was the greatest leap ever taken. The speed of Hanuman's jump pulled blossoms and flowers into the air after him and they fell like little stars on the waving treetops. The animals on the beach had never seen such a thing; they cheered Hanuman, then the air burned from his passage, and red clouds flamed over the sky . . ."
Because of this great leap, the yoga pose of the full split is named after him, Hanumanasana.
There is a beautiful story about Hanuman that I tell my students sometimes. After the great war was over and Sita was safe, Sita gave Hanuman a necklace of priceless pearls as a reward for his heroism and devotion. In front of the assembled nobles, Hanuman pulled the necklace apart, holding each beautiful pearl up to his ear, shaking it, then throwing it to the ground in disgust.
"Hanuman, you stupid monkey!" Sita said. "What are you doing?"
"I wanted to see if the pearls were saying the name of Rama," Hanuman replied. "Only something which says the name of the Lord has meaning to me."
"A pearl is an inanimate object. It cannot speak," said Sita.
But Hanuman countered, "Everything that is saturated with the love of God speaks his name." And Hanuman pulled a handful of hair from his chest and held it to Sita's ears. Every hair on Hanuman's body was softly chanting "RAM."
He ripped his chest open. In his heart was an image of Rama and Sita.