The Omura family traced it's roots back to the 10th Century, when Fujiwara (Ômura) Naozumi settled in Kyushu and later achieved a certain modicum of local influence. Following the Onin War (1467-77) the Sonogi peninsula was divided into a myriad number of petty fiefdoms and the Omura struggled for dominance. In 1474 the neighboring Arima dealt Omura Sumiyoshi a defeat and afterwards exerted considerable influence over the Omura clan. Omura Sumisaki adopted a son of Arima Haruzumi, an event that was to cause the adoptee in question, Sumitada, much difficulty in his own rule. Haruzumi's natural son, Takaaki, had been disinherited in the move, and after ending up in the Goto clan was extremely hostile towards his former family. In fact, Sumitada had to contend with the resentments of a number of local lords, all of whom were in some way kinsmen, including Saigo Sumitaka (a brother-in-law) and Fukahori Sumikata. In addition, the Matsuura and Arima pressed the Omura's borders; yet the greatest threat to Sumitada was Ryuzoji Takanobu, the most powerful daimyo in Hizen.
Faced with the seemingly inevitable fall of the Omura, Sumitada turned to the only party that seemed capable of providing him with telling assistance - the Jesuits. In 1562 he allowed the Christian priests to preach in his domain and gave Portuguese traders special privileges in the port of Yokoseura; the following year Sumitada became the first Christian Daimyo, baptized with the name Dom Bartolomeu in June. Unfortunately, Omura's religious and political workings initially bore bitter fruit; the same year Sumitada was baptized, Goto Takaaki rose against him and in the course of the struggle Yokoseura was destroyed. The event seemed to presage the fall of the Omura, and in 1566 Sumitada was forced to flee Aonogi Castle - his headquarters. Yet the Portuguese returned and with the weapons they supplied, Sumitada was able to retake Sonogi and stabilized his position. Omura managed to fend off his many rivals for the next two decades and Portuguese vessels continued to call at Omura ports. To a greater or lesser extent the Omura-Jesuit pact was beneficial to Sumitada, even if it provoked families already hostile to him. In 1572 Saigo Sumitaka led a coalition of Omura's enemies against Sumitada, a threat Sumitada countered with the help of four Portuguese warships in 1574. From the Portuguese point of view, Sumitada's conversion was an encouraging development but not altogether fruitful-that is, until 1580. By that year, Ryuzoji Takanobu had become the most dynamic lord of northern Kyushu, and his advances into the Sonogi area compelled Sumitada to make a remarkable donation to the Jesuits. On 9 June he ceded rights to the port of Nagasaki, including the transfer of all judicial authority to the Jesuits.
This dramatic move followed in the wake of two Ryuzoji incursions (1577, 78) and was not made so much to preserve the survival of the Omura house as to preserve the Christian presence in Hizen. Above and beyond any possible pious motivations, Sumitada stood to gain much through continued trade with the Portuguese, especially if this were combined with an end of the war with the Ryuzoji. Concerned that Takanobu would drive out the foreigners once the Omura submitted, Sumitada officially 'gave' Nagasaki to the Jesuits, maintaining the rights to collect duty tariffs on the goods that passed through the port. Later that year, Omura went to Saga and submitted to Ryuzoji.
Takanobu hesitated to confront the Portuguese directly, as the power of these 'Southern barbarians' was still something of an unknown element. Just as Sumitada had hoped, Takanobu left Nagasaki alone, leaving the Jesuits to report their unexpected boom to an amazed Rome.
Omura was now a vassal of the Ryuzoji and finally allowed some breathing room. Takanobu turned his eye on the Arima of the Shimabara peninsula, a clan who, like the Omura, had turned to the foreigners for assistance. In 1584 Shimazu Yoshihisa an expeditionary force to Shimabara to assist the reeling Arima, prompting Takanobu to personally lead an army to the area. Sumitada was summoned to lead his own men in support, but was late in taking to the road and managed to miss the decisive Battle of Okinanawate. Takanobu was killed during the battle and the political picture in Hizen changed drastically.
In 1587 Toyotomi Hideyoshi invaded Kyushu and the Omura submitted, though they suffered the loss of the Nagasaki trade. Sumitada died that same year and was succeeded by his son Yoshiaki (1568-1615). Like his father, Yoshiaki was a Christian, and in that capacity was known as Dom Sancho. Yoshiaki served in the 1592 Korean invasion, leading 1,000 men under Konishi Yukinaga. In 1600 he elected to remain neutral during the Sekigahara campaign and as a result was ordered to retire in favor of his son Suminobu. Although baptized in his youth, Suminobu persecuted those Christians still residing in Omura and helped put down the Shimabara Rebellion (1637-38). The Omura stood as a daimyo house until the fall of the Tokugawa shogunate and the abolishment of the han in the 19th Century.