Kashyapa (Sanskrit कश्यप kaśyapa) was an ancient sage (rishis), who is one of the Saptarshis in the present Manvantara; with others being Atri, Vashishtha, Vishvamitra, Gautama, Jamadagni,Bharadwaja  
He was also the author of the treatise Kashyap Samhita, or Braddha Jivakiya Tantra, which is considered, a classical reference book on Ayurvedaespecially in the fields of Ayurvedic pediatrics, gynecology and obstetrics. It can be safely assumed that there were many Kashyaps and the name indicates a status and not just one individual.

He was the father of the Devas, Asuras, Nagas and all of humanity. He married Aditi, with whom he fathered Agni, the Adityas, and most importantly LordVishnu took his fifth Avatar as Vamana, the son of Aditi, in the seventh Manvantara.  With his second wife, Diti, he begot the Daityas. Diti and Aditi were daughters of King Daksha Prajapati and sisters to Sati, Shiva's consort. Kashyap received the earth, obtained by Parashurama's conquest of KingKartavirya Arjuna and henceforth, earth came to be known as "Kashyapi".
Birth and Lineage
                  Kashyap was one of the Saptarshi Brahmins. According to Hindu Mythology, he is the son of Marichi, one of the ten sons (Manasa-putras) of the Creator Brahma. The Prajapati Daksha gave his thirteen daughters (Aditi, Diti, Kadru, Danu, Arishta, Surasa, Surabhi, Vinata, Tamra, Krodhavaśā, Ida, Khasa and Muni [4] in marriage to Kashyap. 
His sons from Diti were, Hiranyakashipu and Hiranyaksha and a daughter Sinhika, who later became the wife of Viprachitti. Hiranyakashipu had four sons, Anuhlada, Hlada, Prahlada, and Sanhlada, who further extended the Daityas. His sons from Aditi or Adityas (Sons of Aditi) were, Aṃśa, Aryaman, Bhaga, Dhūti, Mitra, Pūṣan, a daughter Bhumidevi, Śakra, Savitṛ, Tvaṣṭṛ,Varuṇa, Viṣṇu, and Vivasvat or Vivasvan,  who went on to start the Solar Dynasty (Suryavansha), which later came to be known as Ikshvaku dynasty, after his great grandson, King Ikshvaku, whose subsequent kings were, Kukshi, Vikukshi, Bana, Anaranya, Prithu, Trishanku, and finally King Raghu, who gave it the name, Raghuvansh (Dynasty of Raghu), and then further leading up to Lord Ram, the son of Dashrath. 
Garuda and Aruna are the sons of Kashyap from his wife, Vinata  The Nāgas (serpents) are his sons from Kadru.The Danavas are his sons from Danu.The Bhagavata Purana states that the Apsaras were born from Kashyap and Muni.Uttar Ramayana says Diti had a son named Maya who was the lord of Daityas In the family line of Kashyap, along with him there are two more discoverers of Mantras, namely, his sons Avatsara and Asita. Two sons of Avatsara, namely, Nidhruva and Rebha, are also Mantra-seers. In the Manvantara period named 'Svarochisha', Kashyap was one of the seven Sages (saptarishi) for that manvantara. The Indian valley of Kashmir in the Himalayas is named after him.Kashyap In Buddhism
In the Buddhist Vinaya Pitaka of the Mahavagga (I.245) section the Buddha pays respect to Kashyap by declaring that the Veda in its true form was declared to the Vedic rishis "Atthako, Vâmako, Vâmadevo, Vessâmitto, Yamataggi, Angiraso, Bhâradvâjo, Vâsettho, Kassapo, and Bhagu"  and because that true Veda was altered by some priests he refused to pay homage to the altered version. 
Kashyap in SikhismIn Brahm Avtar composition present in Dasam Granth, Second Scripture of Sikhs, Guru Gobind Singh mentioned Rishi Kashyap, as second avtar of Brahma . According to him, Rishi Kashyap had great knowledge of Vedas and interpreted it very thoughtfully to whole world which bring them internal relief . He married with four wives, Banita, Kadru, Diti and Aditi and have many children out of them some remain religious(Deities) and other became irreligious(Demons).Kashyap and KashmirThe Valley of Kashmir got its name from Kashyap Rishi .According to the Hindu mythology, the Kashmir valley was a vast lake called Satisaras, named after Sati or Parvati the consort ofShiva. The lake was inhabited by the demon Jalodbhav. The Nilamat Puran of the 7thCentury mentions the region being inhabited by two tribes - the Nagas and the Pisachas. The lake was drained off by leader of the Nagas called Ananta (Anantnag region of Kashmir is named after him) in order to capture and kill the demon. Ananta later names the valley as Kashyap-mira after his father Kashyap. Kalhana in Rajatarangini (The River of Kings) also mentions Prajapati Kashyap killing Jalodbhava with the help of Brahma, Vishnu and Shiva. The lake was then drained and comes to be known as Kash-mira after the Rishi Kashyap. Kashyap gotraKashyap is a gotra. Several Indian and non-Indian communities claim descent from the Vedic Rishis. A person of Kashyap Gotra is a person who traces or claims to trace his descent from the ancient sage Kashyap and Suryavansh.