The U.S. government estimates the total population at 68.1 million (midyear 2021).  ccording to a January 2020 report released by the government-appointed Observatory for Secularism, based on a poll conducted in cooperation with polling company Viavoice, approximately 47 percent of respondents identify as Catholic, 3 percent Muslim, 3 percent Protestant, 2 percent Buddhist, 1 percent Jewish, 1 percent Christian Orthodox, and 1 percent other religious groups; 34 percent said they have no religious affiliation and 8 percent preferred not to respond.  According to the observatory’s 2019 report, there are 140,000-150,000 Jehovah’s Witnesses and 150,000-300,000 Hindus.  In a poll on secularism released in February and conducted with Viavoice, 35 percent of respondents say they are believers, 30 percent nonbelievers or atheist, 14 percent agnostic, and 13 percent indifferent.  Most observers, including the observatory in its 2019 report, estimate the number of Muslims in the country at three to five million, or between 4 and 7 percent of the population.  According to Church of Scientology leaders, there are approximately 40,000 followers in the country.

A poll by the research firm French Institute of Public Opinion (IFOP) conducted August 24-25 found that 51 percent of respondents said they do not believe in God, and 49 percent said they do.  According to the IFOP poll, the highest percentage of believers (58 percent) was found among those 65 years and older and the lowest (45 percent) among those aged 35-49.  Other age groups were close to evenly split, with a slight majority of nonbelievers.

The U.S. government estimates the total population at 10.3 million (midyear 2021).  According to the most recent census for which results are available (from 2011), 81 percent of the population older than age 15 is Roman Catholic.  Other religious groups, each constituting less than 1 percent of the population, include Orthodox Christians and various Protestant and other Christian denominations, including the Seventh-day Adventist Church, Lutheran Church of Portugal, The Church of Jesus Christ of Latter-day Saints (Church of Jesus Christ), Church of God of the Seventh Day, New Apostolic Church, and the Portuguese Evangelical Methodist Church.  Other religious groups include Muslims, Hindus, Jews, Buddhists, Sikhs, Taoists, Zoroastrians, and Baha’is.  In the census, 6.8 percent of the population said it does not belong to any religious group, and 8.2 percent did not answer the question.  According to the census, nonevangelical Protestants number more than 75,000.  The Muslim community estimates there are approximately 60,000 Muslims, of whom 50,000 are Sunni and 10,000 Shia, including Ismaili Shia.  There are more than 56,000 members of the Eastern Orthodox Church, most of whom are immigrants from Eastern Europe, primarily from Ukraine, and the Church of Jesus Christ estimates it has 45,000 members.  There are more than 163,000 members of other Christian groups, including other evangelical Christians, Baptists, Seventh-day Adventists, other Protestants, and Jehovah’s Witnesses.  The Jewish community leadership estimates the resident Jewish population is approximately 2,000, with half residing in the greater Lisbon area.

According to a survey published by the Pew Research Center in 2018, 77 percent of the population identifies as Roman Catholic, 4 percent as Protestant, and 4 percent as “other,” while 15 percent are religiously unaffiliated, a group that includes individuals who identify as atheist, agnostic, or “nothing in particular.”