HONG KONG — President Tsai Ing-wen of Taiwan offered a formal apology on Monday to aboriginal peoples for centuries of “pain and mistreatment,” and she promised to take concrete steps to rectify a history of injustice.

In a ceremony at the presidential office in Taipei attended by aboriginal community leaders, she said that although Taiwan had made efforts to end discrimination against hundreds of thousands of indigenous people, a formal apology was necessary.

“Unless we deny that we are a country of justice, we must face up to this history,” Ms. Tsai said. “We must tell the truth. And then, most importantly, the government must genuinely reflect on this past.”

Taiwan has 540,000 residents who are members of aboriginal groups, or about 2 percent of the population of 23 million. The Council of Indigenous Peoples officially recognizes 16 groups, with three — the Amis, Atayal and Paiwan — making up 70 percent of the total indigenous population.