The Nguyễn lords (, 主阮; 1558–1777, 1780–1802), also known as the Nguyễn clan (阮氏, Nguyễn thị), were the rulers of southern Đại Việt during the Revival Lê dynasty and ancestors of Nguyễn dynasty's emperors. The territory they ruled was known contemporarily as Đàng Trong (Inner Realm) and by Europeans as Cochinchina, in opposition to the Trịnh lords ruling northern Đại Việt, known then as Đàng Ngoài (Outer Realm). Both Nguyễn and Trịnh lords were de jure subordinates of the Lê dynasty.
The Nguyễn lords were members of the House of Nguyễn Phúc. While they recognized the authority of and claimed to be loyal subjects of the revival Lê dynasty, they were de facto rulers of southern Đại Việt. Meanwhile, the Trịnh lords ruled northern Đại Việt in the name of the Lê emperor, who was in reality a puppet ruler. They fought a series of long and bitter wars that pitted the two halves of Vietnam against each other. The Nguyễn were finally overthrown in the Tây Sơn wars, but one of their descendants would eventually come to unite all of Vietnam. Their rule consolidated earlier southward expansion into Champa and pushed southwest into Cambodia.
Origin
The Nguyễn lords traced their descent from a powerful clan originally based in Thanh Hóa Province. The clan supported Lê Lợi in his successful war of independence against the Ming dynasty. From that point on, the Nguyễn were one of the major noble families in Vietnam. Perhaps the most famous Nguyễn of this time was Nguyễn Thị Anh, the queen-consort for nearly 20 years (1442–1459).
Nguyễn Kim restores the Lê dynasty
In 1527, Mạc Đăng Dung overthrew the emperor Lê Cung Hoàng and established a new dynasty- the Mạc dynasty. The Trịnh and Nguyễn lords fled to Thanh Hóa province and refused to accept the rule of the Mạc. All of the region south of the Red River was under their control, but they were unable to dislodge the Mạc from Thăng Long for many years. During this time, the Nguyễn–Trịnh alliance was led by Nguyễn Kim; his daughter Nguyễn Thị Ngọc Bảo was married to the Trịnh clan leader, Trịnh Kiểm.
Trịnh seizes power over the Lê dynasty
In 1533 the Lê dynasty was restored and the Mạc driven into exile in the far north. However, the emperor Lê Trang Tông was a powerless figurehead- true authority lay in the hands of Nguyễn Kim. In 1543, Nguyễn Kim captured Thanh Hóa from Mạc loyalists. Dương Chấp Nhất, commander of Mạc forces in the region, decided to surrender his troops to the advancing Nguyễn forces. When Kim seized Tây Đô citadel and was on route to attack Ninh Bình, in 20 May 1545, Dương Chấp Nhất invited Kim to visit his military camp. In the hot temperature of summer, Dương Chấp Nhất treated Kim with a watermelon. After the party, Kim felt ill after returning home and died the same day. Dương Chấp Nhất later returned to the Mạc dynasty. The records of the Đại Việt sử ký toàn thư and Đại Nam thực lục both suggest that Dương Chấp Nhất tried to assassinate the emperor Lê Trang Tông by pretending to surrender. However, the plot was unsuccessful, and then he changed his target to Nguyễn Kim, who was in charge of power and the military.
After the death of Kim, the imperial government was plunged into chaos. Kim's eldest son Nguyễn Uông initially took power, but he was soon secretly assassinated by his brother-in-law Trịnh Kiểm who assumed control of the government.
Nguyễn Hoàng as governor of Thuận Hóa and Quảng Nam province
Kim's second son Nguyễn Hoàng feared that he would suffer his brother's fate; hence, he attempted to flee the capital to avoid assassination. Later, he asked his sister Nguyễn Thị Ngọc Bảo (wife of Trịnh Kiểm) to ask Kiểm to appoint him to be the governor of Đại Việt's southern frontier Thuận Hóa in what is modern-day Quảng Bình to Quảng Nam provinces, land that once belonged to the Cham. Thuận Hóa was still regarded as uncivilised land, and simultaneously, Trịnh Kiểm also sought to remove the power and influence of Nguyễn Hoàng in the capital city; so, he agreed to appoint Nguyễn Hoàng as governor of these distant lands.
In 1558, Nguyễn Hoàng and family and his loyal generals moved to Thuận Hóa to take his position. Arriving at Triệu Phong District, he made the place his new capital and constructed a new palace.
In March 1568, Emperor Lê Anh Tông summoned Hoàng for a meeting at Tây Đô and met Trịnh Kiểm at his personal mansion. Kiểm trusted Nguyễn Hoàng, so he arranged for the emperor to additionally appoint Hoàng governor of Quảng Nam as well.
In 1636, Nguyễn Hoàng moved his base to Phú Xuân (modern Huế). Nguyễn Hoàng slowly expanded his territory further south, while the Trịnh lords continued their war with the Mạc dynasty for control over northern Vietnam.