Gorakhnath:his legendary footprints are all over the country

Matsyendranath: guru to Gorakhnath (below)

Amongst the greatest Siddhars is Korrakar , who in the rest of India is venerated as the nath yogi Gorakhnath. His footprints are all over this vast country. Almost all regions and states claim him as their own. From the northwest, to the east, to the southern tip of India, nay even beyond, at Sri Lanka, his influence has been felt. Even today the school of yogis referred as Nath yogis are unusual warrior like yogis, who do not bow to known sets of political compliance. Since they do not identify with religious sects or castes, they reflect an India which is spiritual outside these confines.

Here is a powerful quote attributed to him and that explains the core of yoga philosophy even today.

The four varna (castes) are perceived to be located in the nature of the individual, i.e. Brahmana in sadacara (righteous conduct), Ksatriya in saurya (valor and courage), Vaisya in vyavasaya (business), and Sudra in seva (service). A yogin experiences all men and women of all races and castes within himself. Therefore he has no hatred for anybody. He has love for every being.

— Gorakhnath, Siddha Siddhanta Paddhati III.6-8

Many legends are attributed to him, as evidence of his yogic prowess, usually feats to show how he aided is disciples or devotees in difficult circumstances.  Many of these stories also reflect the fact that he was regarded as a great healer. 

His origins were very humble. Though there are different stories of his origin, all have a common detail: he was discovered as a baby left on a dung hill. And he was the direct disciple of the powerful yogi Matsyendranath, after whom the famous spinal twist pose in yoga is named.