The Pahang Sultanate (Malay: Kesultanan Pahang, Jawi: كسلطانن ڤهڠ‎) also referred as the Old Pahang Sultanate, as opposed to the modern Pahang Sultanate, was a Malay Muslim state established in the eastern Malay Peninsula in the 15th century. At the height of its influence, the sultanate was an important power in Southeast Asia and controlled the entire Pahang basin, bordering the Pattani Sultanate to the north and the Johor Sultanate to the south. To the west, its jurisdiction extended over parts of modern-day Selangor and Negeri Sembilan.

The sultanate has its origin as a vassal of Melaka, with its first sultan being a Melakan prince, Muhammad Shah, himself the grandson of Dewa Sura, the last pre-Melakan ruler of Pahang. Over the years, Pahang grew independent from Melakan control and at one point even established itself as a rival state to Melaka until the latter's demise in 1511. During this period, Pahang was heavily involved in attempts to rid the peninsula of the various foreign imperial powers; Portugal, the Netherlands and Aceh. After a period of Acehnese raids in the early 17th century, Pahang entered into the amalgamation with the successor of Melaka, Johor, when its 14th sultan, Abdul Jalil Shah III, was crowned the 7th Sultan of Johor. After a period of union with Johor, it was eventually revived as a modern sovereign Sultanate in the late 19th century by the Bendahara dynasty.

Muzaffar Shah, the 5th Sultan of Melaka who reigned from 1445 to 1458 refused to acknowledge the suzerainty of Ligor over his country. The Ligorians, in assertion of their claim, sent an invading army led by Awi Chakri, overland to Melaka. The invaders, who were aided by auxiliaries from the Pahang Kingdom, followed the old route by the Tembeling, Pahang and Bera rivers. They were easily defeated and fled back by the same route. Subsequently, they attempted a naval invasion, and were again beaten. Muzaffar Shah then conceived the idea of checking Ligorian pretensions by attacking the Ligor vassal state, Pahang. An expedition was organised by Muzaffar's son, Raja Abdullah and was personally led by the Melakan Bendahara Tun Perak with two hundred ships, proceeded to Pahang and conquered it in 1454. The last ruler of the kingdom, Dewa Sura was captured and carried together with his daughter Putri Wanang Seri to Melaka.

The Sultan of Melaka appointed Sri Bija Diraja Tun Hamzah, the commander of the army in the conquest, as the governor of Pahang, and permitted him the privilege, once he was out of Melakan waters, of using six of the eight instruments that made up nobat band, and of having a pair of fringed umbrellas borne over him. Sri Bija Diraja accordingly proceeded to Pahang which he governed for several years. Once a year he visited Melaka to show respect to his sovereign.

In the year that Pahang was conquered, Raja Abdullah married Putri Wanang Seri, the daughter of Dewa Sura, whose name had been changed Putri Lela Wangsa, probably on conversion to Islam. By her he had two sons Raja Ahmad and Raja Muhammad.

Muzaffar Shah died around 1458 and was succeeded by Raja Abdullah who was styled Sultan Mansur Shah. As his sons grew up, the new ruler paid special favour to Raja Muhammad and designated him as his successor. When Raja Muhammad was about fifteen years old he was riding past a group of boys who were engaged in a sepak raga game, when a misdirected ball kicked by Tun Besar, the Bendahara's son displaced Muhammad's headdress. In a rage he drew his kris and killed Tun Besar.

The Bendahara's people flew to arms to avenge Tun Besar's death, but were restrained by the Bendahara who warned them against any measures that might be construed as treason against the Sultan. However, the Bendahara and his people vowed that the Raja Muhammad should never rule over them. Sultan Mansur, after hearing their complaint, agreed that Raja Muhammad should be exiled from Melaka. He recalled Sri Bija Diraja from Pahang and commanded him to escort Muhammad to that country and install him as their Sultan.

Accompanied by Tun Hamzah who was appointed Bendahara for the new kingdom, Seri Akar Raja as his Hulubalang, a Penghulu Bendahari, a Temenggung, and a hundred youths and a hundred maidens of noble family, Raja Muhammad proceeded to Pahang where he was installed as sultan around 1470 with the title Sultan Muhammad Shah. The boundaries of his kingdom extended from Sedili Besar to the south up to border with Terengganu to the north. The first Melakan ruler of Pahang, appears to have settled at Tanjung Langgar in Pekan, the old seat of the pre-Melakan rulers.