The was a Japanese samurai family whose power stretched from the Kamakura period through the Sengoku period, spanning over 400 years. The clan's hereditary lands lay in Kyà «shà «.
The first family head, à Âtomo Yoshinao (1172âÂÂ1223), took the name from the à Âtomo territory in Sagami Province. The clan claims descent from Emperor Seiwa (850-881) through the Seiwa Genji lineage of the Minamoto clan. Although the clan genealogy claims Yoshinao to be an illegitimate son of Minamoto no Yoritomo, it has been concluded that he was in fact a descendant of the Fujiwara clan.
Following the establishment of the Kamakura shogunate in 1185, Yoshinao was granted the post of Governor (Shugo) of Bungo and Buzen Provinces in Kyà «shà «.
à Âtomo Yoshinao's descendants served as Governor of Buzen and Bungo Provinces for generations further establishing the power of à Âtomo clan in these two provinces. The clan would expand their power in Bungo Province along with the Shiga clan, founded by Yoshinao's eighth son Shiga Yoshisato, that had settled there earlier.
As the à Âtomo were one of the major clans of Kyà «shà «, along with the Shà Âni and the Shimazu, they had a central role in organizing efforts against the Mongol invasions of Japan in 1274 and 1281.
They also played an important role in the establishment of the Ashikaga shogunate, in the 1330s. à Âtomo warriors fought alongside those of Ashikaga Takauji and enabled him to win a number of key battles, including the battle of Sanoyama; this helped to ensure them powerful government positions in the new shogunate. Following the unrest of the Nanboku-chà  period, the clan became an influential Shugo Daimyo family in Bungo, Buzen, and Chikugo Provinces during the Muromachi period.
Yoshinaga, 19th generation descendant of Yoshinao, along with his son Yoshiaki further became Sengoku period Daimyos. At the time of 21st generation Yoshishige, the à Âtomo clan reached its zenith by expanding its power to Hizen, Higo, and Chikuzen Provinces. At its zenith, the à Âtomo clan ruled six provinces (Buzen, Bungo, Hizen, Higo, Chikuzen and Chikugo) and two half-provinces (Hyà «ga and Iyo).
Towards the end of the 16th century, the à Âtomo fought both the Shimazu and Mà Âri clans, the latter of whom were expert sailors. Though they did not play a major role in the campaigns of Tokugawa Ieyasu which ended the Sengoku period, they did retain their domains into the Edo period.
A powerful clan throughout the Sengoku period (1467âÂÂ1573), the à Âtomo are especially notable as one of the first clans to make contact with Europeans, and to establish a trade relationship with them. In or around 1542, three Portuguese ships were carried by a typhoon to the island of Tanegashima, just off the coast of Kyà «shà «. Within ten years, trade with the Portuguese was fairly regular and common in Kyà «shà «.
The Jesuit missionary Francis Xavier arrived in Japan in 1549, and soon afterwards met with à Âtomo Sà Ârin (Yoshishige), shugo of Bungo and Buzen Provinces, who would later be described by Xavier as a "king" and convert to Roman Catholicism in 1578. à Âtomo was eager to secure for his clan further trade and contact with the Portuguese, seeing the technological and, more importantly perhaps, economic benefits that could be derived.
In 1552, emissaries from the à Âtomo clan traveled to Goa with Xavier, to meet with the Portuguese Governor of India. Xavier and other Jesuit missionaries would return to Kyà «shà «, traveling and proselytizing; the à Âtomo were always well-disposed towards them, and they saw some success in Bungo as a result, converting many Japanese to Christianity.
Otomo is a playable nation in the grand strategy games Europa Universalis IV, Sengoku as well as in '.