Islam is the official religion in Kuwait, with the majority of the citizen population being Muslim. Kuwait has a native Christian community; there are between 259-400 Christian Kuwaiti citizens. There is a small number of Bahá'í Kuwaiti citizens. Most expats in Kuwait are Muslim, Hindu, Christian or Buddhist.
Most of Kuwait's citizen population is Muslim; there are no official figures, but it is estimated that 60%-65% are Sunni and 35%-40% are Shias. Some other minor Muslim sects do exist in Kuwait's society, but in very small or rare numbers. There are no estimates of the number of non-citizen Sunnis, but there are an estimated 100,000 non-citizen Shia.
In 2001, there were 525,000 Sunni Kuwaiti citizens, 300,000 Shia Kuwaiti citizens and 820,000 Kuwaiti citizens in total thus Sunnis formed 64% and Shias formed 36.5% of the Kuwaiti citizen population. In 2002, the US Department of State reported that Shia Kuwaitis formed 30%-40% of Kuwait's citizen population, noting there were 525,000 Sunni Kuwaiti citizens and 855,000 Kuwaiti citizens in total (61% Sunnis, 39% Shias). In 2004, there were 600,000 Sunni Kuwaitis citizens, 300,000-350,000 Shia Kuwaiti citizens and 913,000 Kuwaiti citizens in total. In 2007, there were 70 % of citizens that belong to the Sunni branch of Islam while most of remaining 30% of citizens are Shia Muslims. 
Christianity is a minority religion in Kuwait. Kuwait has a native Christian community, there are between 200 and 400 Christian Kuwaiti citizens. In 2014, there were 259 Christian Kuwaitis residing in Kuwait. Kuwait is the only GCC country besides Bahrain to have a local Christian population who hold citizenship. Of the non-citizen population, there are an estimated 600,000 Christians in Kuwait. The government-recognized Christian churches include the Roman Catholic Church, the Coptic Orthodox Church, the National Evangelical Church Kuwait (Protestant), the Armenian Apostolic Church, the Greek Orthodox Church, the Greek Catholic (Melkite) Church, and the Anglican Church. There are also many Christian religious groups not officially recognised by the government with smaller populations, including the Indian Orthodox, Mar Thoma, The Church of Jesus Christ of Latter-day Saints (Mormons), and Seventh-day Adventist Church. Unrecognized groups are generally free to worship in private. There are also a number of believers in Christ from a Muslim background in the country, though many are not citizens. A 2015 study estimates some 350 such Christians in the country.
There is a small number of Bahá'í Kuwaiti citizens. While the official 2013 census only shows three religion categories: "Muslim", "Christian" and "Other", with only 18 people in the other category, another source states that there are around 400 Bahá'ís in total in Kuwait.
There were some Kuwaiti Jews before the 1950s, however all Jewish families left Kuwait by the 1980s. There are currently no known Jewish citizens and an estimated few dozen Jewish foreign resident workers.
There are an estimated 300,000 non-citizen Hindus.
100,000 non-citizen Buddhists reside in Kuwait.
There are 10,000 Sikhs in Kuwait.
Shiites comprise 60 percent of the population in Bahrain, 40 percent in Kuwait, 14 percent in Saudi Arabia, and 35 percent in Lebanon.