Razadarit (Burmese: ရာဇာဓိရာဇ် [jàza̰dəɹɪ̀ʔ]; Thai: ราชาธิราช, rtgs: Rachathirat; Sanskrit: राजाधिराज Rājādhirāja "King of Kings"; 1368–1421) was the ninth king of the Hanthawaddy Pegu Kingdom in Burma from 1384 to 1421. Considered one of the greatest kings in Burmese history, he successfully reunified all three Mon-speaking regions of southern Burma (Myanmar), and fended off major assaults by the Burmese-speaking northern Kingdom of Ava (Inwa) in the Forty Years' War (1385–1424).

When Razadarit became the ruler of Hanthawaddy in 1384, the 16-year-old boy-king held just the Pegu (Bago) province while the other two major Mon-speaking regions of the Irrawaddy delta and Martaban (Mottama) were in open rebellion. By his sheer will and military leadership, he defeated Ava's first wave of invasions in the 1380s, and by 1390, was able to reunify all three Mon regions. During the second half of the Forty Years' War, he met Minkhaung I of Ava and his son Minye Kyawswa head-on in Lower Burma, Upper Burma, and Arakan.

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