King Yangwon of Goguryeo (died 559) (r. 545–559) was the 24th ruler of Goguryeo, the northernmost of the Three Kingdoms of Korea. He was the eldest son of King Anwon. During Yangwon's reign, Goguryeo gradually grew weaker and was obliged to take various urgent measures to block foreign invasions, eventually losing the Seoul region to the alliance of the other two Korean kingdoms.
He was confirmed as heir to the throne in 533, the third year of King Anwon's reign. Although he was the heir, it is said that the was not able to simply assume power after his father's death. Anwon had three wives, and because the first did not bear him a son, the other queens strove to put their son on the throne. Yangwon's supporters won the military struggle and he was able to succeed to the throne.
Preparing for war in 547, the king rebuilt Baegam fortress and repaired Sin fortress. In 548, he sent 6,000 soldiers against Baekje's Doksan fortress but the Silla general Ju Jin led a relief army and the Goguryeo assault failed. In 550, Baekje invaded and sacked Dosal fortress. Goguryeo counterattacked and struck Baekje's Geumhyeon fortress, but Silla took advantage of this to seize two more Goguryeo castles.
In 551, the emerging empire of the Göktürks invaded from Central Asia and laid siege to Sin fortress; unable to take it, they attackd Baegam fortress instead. At this, King Yangwon sent his general Go Heul and 10,000 troops against the Göktürks; they killed or captured 1,000. In the same year, Silla invaded once again and captured ten districts of the present-day Seoul region. In 552, Jangan fortress was built. In 554, Yangwon's forces attacked Ungcheon fortress in Baekje, but failed to take it.
In 557, Yangwon designated the prince Go Yang-seong as heir to the throne. In the tenth lunar month of that same year, the commander Gan Juri of Hwando fortress rebelled, but the rebellion was put down and he was executed. King Yangwon died in 559, after fifteen years on the throne.