賽德克，在賽德克語中意指「真正的人」，因其文化習俗與泰雅相似，自日本侵佔臺灣時期起，就一直被歸屬為泰雅的亞族，直至2008年4月才被確認為賽德克，成為臺灣少數民族的第14個族群。
賽德克氏族發源於南投仁愛鄉的濁水溪上遊，並在此分成德克搭雅、都達、太魯閣三個最早的社群。大約18世紀，這三個社群因為人口增加、土地不敷使用，各有一部份人翻越中央山脈分水嶺，遷徙到花蓮縣境內，形成了居住在南投仁愛鄉的西賽德克，以及居住在花蓮縣秀林、萬榮、卓溪鄉的東賽德克。而每一地方族群之下又各分成三個社群，總數共有六個社群。其中東賽德克德魯固群已在2004年另劃歸為「太魯閣」族群。
賽德克人的傳統生活方式和習俗，是重視男獵女織的男女分工，也擁有紋面成年禮及嚴守祖靈禁忌等傳統習俗。部落是最基本的自治單位，屬於沒有世襲頭目的平權社會，由領導能力強的人出任部落領袖，狩獵、出草也由英勇的族人擔任領袖。當遇到部落有重大事情時，則是由長老會議決策，部落組織對內具有保護功能，對外則負有與其它部落保持聯絡的責任，是一個同地域同盟共利的團體。
賽德克也擁有泰雅族群類似的兼有宗教和互助性質的「嘎嘎」團體，只是賽德克語稱之為「嘎呀」。賽德克的嘎呀成員幾乎都屬同一部落，很少出現泰雅那種跨部落的情況。同一個嘎呀的成員之間，有共同從事祭祀、協助參與復仇、集體分攤賠償的義務，而且「嘎呀」也可解釋為部落的習慣法律或傳統禁忌。
Sediq / Sejiq / Seediq
Sediq, Sejiq or Seediq refers to 「true person」 in the tribe’s native language. Due to similarities with the Atayal in terms of culture and customs, scholars originally defined the Sediq as a branch of the Atayal tribe. However, in April of 2008, the Sediq was recognized as Taiwan’s 14th official tribe.
The Sediq were originally located along the upper reaches of the Zhuoshui River in Renai Township of Nantou County. From there, they branched out into three groups: Tkdaya, Teuda and Truku. Around the 18th century, due to a growing population, some members of the Sediq tribe crossed the Central Mountain Range to arrive in present-day Hualien County. Those that remained in Renai Township were referred to as the western Sediq and those that resided in Hualien were referred to as the eastern Sediq. In 2004, the eastern Sediq were incorporated into the Truku.
Traditionally, the males hunted and the females wove cloth. The Sediq practiced facial tattooing as part of the coming-of-age rites and observed the taboos and lessons passed down from the ancestors. The society was based on equal rights and there was no chieftain system. Those with outstanding qualities were chosen to lead the village. Hunting and warring expeditions were led by the bravest warriors. If the village met with a major crisis the elders』 council would decide on a solution.
Similar to the 「Gaga」 of the Atayal tribe, the Sediq had a group, called the 「Gaya」 to oversee the religious practices and customs. The 「Gaya」 can also be interpreted to mean the common law or traditional taboos of the village.