Nyaungyan Min (Burmese: ညောင်ရမ်းမင်း [ɲàʊɰ̃jáɰ̃ mɪ́ɰ̃]; 8 November 1555 – 5 November [O.S. 26 October] 1605) was king of the Toungoo dynasty of Burma (Myanmar) from 1599 to 1605. He is also referred to as the founder of the restored Toungoo dynasty or Nyaungyan dynasty for starting the reunification process following the collapse of the First Toungoo Empire.

A son of King Bayinnaung by a minor queen, Nyaungyan gradually emerged as a power in Upper Burma in the mid-1590s. When major vassal rulers renounced their ties with King Nanda in 1597, he too broke away by seizing Ava (Inwa). But he stayed out of myriad wars in the low country. Instead, he methodically consolidated his base in the upcountry, and went on to acquire the surrounding cis-Salween Shan states until his death in 1605. He also rebuilt the economy of Upper Burma, and (re-)established several social, financial and military standards, many of which would be retained to the end of the Toungoo dynasty in 1752. His efforts paved the way for his eldest son and successor Anaukpetlun to restore major portions of the Toungoo Empire in the next two decades.

He was born Shin Thissa (ရှင်သစ္စာ, [ʃɪ̀ɴ θɪʔsà]) to Lady Khin Pyezon and King Bayinnaung on 8 November 1555. He had an elder brother, Shin Ubote. He was one of the 91 children born to minor queens, who were ranked below the six children by the three senior queens. Indeed, Thissa had to wait until he was 25 to get a governorship. On 8 February 1581, the king appointed Thissa to succeed Ubote, who died in January 1581, as governor of Nyaungyan, a small town in present-day Meiktila District, south of Ava (Inwa). The small town governor was married to his half sister Khin Hpone Myint, who like him was a child of a junior queen. (Khin Hpone Myint's name is sometimes reported as "Khin Hpone Myat".)The couple had been married since 25 February 1577, and had a 3-year-old child, one Thakin Lat.

It was at Nyaungyan that Thissa slowly made his name, and came to be known as Nyaungyan Min (Lord of Nyaungyan). He indirectly benefited from Pegu's troubles in the next decade and a half that saw Pegu's power gradually retrench from its vassal states.

For his first dozen years at Nyaungyan, Thissa was a loyal, if unremarkable, governor. He quietly ruled a small region which fell within the jurisdiction of his half-uncle Thado Minsaw, Viceroy of Ava (Upper Burma). One key decision he made came in 1584 when he sided with King Nanda after Thado Minsaw revolted. He remained a loyal vassal during the Siamese rebellion (1584–93) although it is unclear how much he, a second-tier governor, could have contributed to the war effort. It was only in 1594 after Nanda decided to withdraw central administration from Upper Burma and the Shan states that Nyaungyan emerged as a power in Upper Burma. In December 1593, Nanda recalled Viceroy of Ava Minye Kyawswa II to Pegu to take over as Crown Prince, and more importantly, the king decided not to appoint a replacement viceroy or governor of Upper Burma. Given that Pegu possessed no institutional capacity to directly administer the upcountry, Nanda had essentially chosen to devolve power to myriad minor vassals rather than appoint an effective viceroy or governor who could turn against him. Nanda's paranoia had a basis. His own son Thado Dhamma Yaza III, Viceroy of Prome (Pyay), revolted in April 1595.

Nanda's policy of devolution created a power vacuum in the upcountry which ambitious governors like Nyaungyan now maneuvered to fill. The opportunity for Nyaungyan to come to the forefront came in 1596 when Thado Dhamma Yaza III, the self-proclaimed king of Prome, invaded central Burma. Nanda ordered Nyaungyan to organize a defense. Nyaungyan agreed to follow the order as he could not let anyone else take over central Burma. His forces successfully stopped the Prome advance at Pakhan, a key town on the Irrawaddy about 120 km south of Ava, but could not retake more southerly towns. After the fighting was done, Prome forces had occupied central Burma up to Salin, about 240 km south of Ava. Prome planned to resume the war in the following dry season of 1597–98.

Nyaungyan, whose army essentially controlled the region around Ava, quietly decided to consolidate power for himself. At Pegu, Nanda was desperate to retain Nyaungyan's loyalty. The king awarded Nyaungyan the title of Minye Nandameit (မင်းရဲနန္ဒမိတ်) along with lavish gifts. At the same time, he was suspicious of his stronger vassals' intentions. The king asked Nyaungyan, Minye Thihathu II of Toungoo and Nawrahta Minsaw of Lan Na to send their eldest sons to Pegu, essentially to hold them as hostages. It was a major miscalculation on Nanda's part for he had no real power to enforce his order. Indeed, he could do nothing when the viceroys of Toungoo and Lan Na formally declared independence.

The chronicles say only that Nyaungyan ignored the king's order but do not mention his formal declaration of independence during Nanda's reign. But surviving royal orders from Nyaungyan's court show that he essentially did in 1597. First, he declared without the king's permission on 19 April [O.S. 9 April] 1597 that he would take over Ava, and that he would officially move into the new palace there on 27 August [O.S. 17 August] 1597. According to Than Tun, Nyaungyan "virtually declared" himself King of Ava on 9 May [O.S. 29 April] 1597 in the order announcing the appointment of Maha Okka Dhamma and Maha Okka Thena as chief ministers of his court.