In some countries, religion isn't just a way of life – it's the law.
Some countries are seen as holier-than-thou.

The Jewish homeland of Israel is perceived to be the most religious in the world, according to data from the 2018 Best Countries rankings, a characterization of 80 countries based on a survey of more than 21,000 global citizens. In the survey, respondents answered how closely they related each of the 80 countries to the term "religious," an adjective that Merriam-Webster defines as a "faithful devotion to an acknowledged ultimate reality or deity," but can hold different meanings for different people.

The Basic Law in Israel describes the country as a Jewish state and "protects the freedom of conscience, faith, religion, and worship, regardless of an individual’s religious affiliation," according to the U.S. Department of State's International Religious Freedom Report for 2016. Israel's capital, Jerusalem, is home to significant religious and historic sites such as the Western Wall and Temple Mount – which draws both Jews and Muslims – but the nation has also been rife with violence between Palestinians and Israeli security forces in Israel, Jerusalem, Gaza and the West Bank.

Saudi Arabia and Iran rank No. 2 and No. 3, respectively, in terms of perceived religiosity. Saudi Arabia has a theocratic monarchy with a legal system based on Islamic Shariah law and Islam is the official state religion of Iran.

Data show Islam is spreading, on track to surpass Christianity as the world's biggest religion. While the world’s population is projected to grow 32 percent in the next few decades, the number of Muslims is expected to increase by 70 percent – from 1.8 billion in 2015 to nearly 3 billion in 2060, a 2017 Pew Research Center report found.

Meanwhile, the United States, with freedom to practice religion guaranteed in its Constitution, ranks No. 62. Sweden and Australia are perceived to be the least religious countries at Nos. 79 and 80, respectively.

Below are the 10 countries perceived to be the most religious, and more country-related rankings can be found here.