Altamira is one of one hundred and forty-four municipalities in the state of Pará, in northern Brazil. It has an area of 159,533.73 square kilometres or 61,596.32 square miles, making it the largest municipality by area both in Pará state and Brazil, and until 2009 it was the world's largest municipal subdivision. It occupies 12.8% of the state's territory, 1.8% of Brazil's territory and 0.8% of South America. It also covers a more extensive area than 104 countries, and is comparable to the US State of Missouri or Florida.
Altamira Municipality encompasses the Altamira city and district, the seat of local government, whose majority population lives in urban area, and nine other mostly rural districts, whose urban populations are minorities, and live in inhabited areas spaced by tens or hundreds of kilometers. According to the 2010 Brazilian National Census the municipality had 99,075 inhabitants which grew to 115,969 at the 2020 Census, making a density of only 0.73 inhabitants per square kilometer at the same year. It is home to hundreds of indigenous communities and environmental protection areas.