Religion

=== Demographic classification ===
{{Main|Major religious groups|List of religious populations}}
{{multipleimage
| perrow            = 2
| total_width       = 335
| footer            = Example of followers of popular and [[world religions]], from top-left: [[Christians]], [[Muslims]], [[Hindus]], [[Buddhism|Buddhists]], [[Sikhs]], and [[Jews]].
| image1            = Via Dolorosa, Jerusalem.jpg
| image2            = The Umayyad Mosque, Muslim Women, Damascus, Syria.jpg
| image3            = Hindu marriage ceremony offering.jpg
| image4            = Incense-LE.jpg
| image5            = Sikh people.jpg
| image6            = Western Wall, Jerusalem, (16037897867).jpg
}}

The five largest religious groups by world population, estimated to account for 5.8 billion people and 84% of the population, are Christianity, Islam, Buddhism, Hinduism (with the relative numbers for Buddhism and Hinduism dependent on the extent of [[syncretism]]), and traditional folk religions.

{| class="wikitable sortable"
|-
! Five largest religions
! 2015 (billion)<ref>{{cite web |title=Christians are the largest religious group in 2015 |url=https://www.pewresearch.org/religion/2017/04/05/the-changing-global-religious-landscape/pf_17-04-05_projectionsupdate_grl310px/ |website=Pew Research Center |access-date=8 July 2022 |archive-date=8 July 2022 |archive-url=https://web.archive.org/web/20220708123444/https://www.pewresearch.org/religion/2017/04/05/the-changing-global-religious-landscape/pf_17-04-05_projectionsupdate_grl310px/ |url-status=live }}</ref>
! 2015 (%)
! Demographics
|-
| [[Christianity]]
| 2.3
| 31%
| [[Christianity by country]]
|-
| [[Islam]]
| 1.8
| 24%
| [[Islam by country]]
|-
| [[Hinduism]]
| 1.1
| 15%
| [[Hinduism by country]]
|-
| [[Buddhism]]
| 0.5
| 6.9%
| [[Buddhism by country]]
|-
| [[Folk religion]]
| 0.4
| 5.7%
|
|-
| Total
| 6.1
| 83%
| [[Religions by country]]
|}
[[File:Abraham Dharma.png|thumb|A rough split of the world among belief systems: [[Abrahamic religions|Abrahamic]] in pink, [[Dharmic religions|Dharmic]] in yellow.]]

A global poll in 2012 surveyed 57 countries and reported that 59% of the world's population identified as religious, 23% as [[Irreligion|not religious]], 13% as convinced [[Atheism|atheists]], and also a 9% decrease in identification as religious when compared to the 2005 average from 39 countries.<ref name="gia">{{cite web |url= https://www.wingia.com/web/files/richeditor/filemanager/Global_INDEX_of_Religiosity_and_Atheism_PR__6.pdf |title= Global Index of Religiosity and Atheism |publisher= WIN-Gallup International |date= 27 July 2012 |access-date= 24 August 2012 |url-status=dead |archive-url= https://web.archive.org/web/20120906165952/https://www.wingia.com/web/files/richeditor/filemanager/Global_INDEX_of_Religiosity_and_Atheism_PR__6.pdf |archive-date= 6 September 2012}}</ref> A follow-up poll in 2015 found that 63% of the globe identified as religious, 22% as not religious, and 11% as convinced atheists.<ref name="GallupInt2015">{{cite web|title=Losing our Religion? Two-Thirds of People Still Claim to be Religious|url=https://www.wingia.com/web/files/news/290/file/290.pdf|website=WIN/Gallup International|date=13 April 2015|url-status=dead|archive-url=https://web.archive.org/web/20150430232945/https://www.wingia.com/web/files/news/290/file/290.pdf|archive-date=30 April 2015}}</ref> On average, women are more religious than men.<ref>{{cite web|url=https://www.livescience.com/7689-women-religious-men.html|title=Women More Religious Than Men|work=Live Science|date=28 February 2009|access-date=14 July 2013|archive-date=8 July 2013|archive-url=https://web.archive.org/web/20130708085942/http://www.livescience.com/7689-women-religious-men.html|url-status=live}}</ref> Some people follow multiple religions or multiple religious principles at the same time, regardless of whether or not the religious principles they follow traditionally allow for [[syncretism]].<ref>''Soul Searching: The Religious and Spiritual Lives of American Teenagers'' – p. 77, Christian Smith, Melina Lundquist Denton – 2005</ref><ref>"Christ in Japanese Culture: Theological Themes" in Shusaku Endo's ''Literary Works'', Emi Mase-Hasegawa – 2008</ref><ref>[https://www.christianpost.com/news/new-poll-reveals-how-churchgoers-mix-eastern-new-age-beliefs-42215/ New poll reveals how churchgoers mix eastern new age beliefs] {{Webarchive|url=https://web.archive.org/web/20220122041129/https://www.christianpost.com/news/new-poll-reveals-how-churchgoers-mix-eastern-new-age-beliefs-42215/ |date=22 January 2022 }} retrieved 26 July 2013</ref> Unaffiliated populations are projected to drop, even when taking disaffiliation rates into account, due to differences in birth rates.<ref>{{cite news |title=Islam set to become world's largest religion by 2075, study suggests |url=https://www.theguardian.com/world/2017/apr/05/muslim-population-overtake-christian-birthrate-20-years |access-date=20 March 2021 |work=The Guardian |date=5 April 2017 |language=en |archive-date=14 April 2021 |archive-url=https://web.archive.org/web/20210414064511/https://www.theguardian.com/world/2017/apr/05/muslim-population-overtake-christian-birthrate-20-years |url-status=live }}</ref><ref>{{cite news |title=The Changing Global Religious Landscape |url=https://www.pewforum.org/2017/04/05/the-changing-global-religious-landscape/ |access-date=21 March 2021 |work=[[Pew Research Center]]'s Religion & Public Life Project |date=5 April 2017 |archive-date=28 September 2021 |archive-url=https://web.archive.org/web/20210928225648/http://www.pewforum.org/2017/04/05/the-changing-global-religious-landscape/ |url-status=live }}</ref>

Scholars have indicated that [[Desecularization|global religiosity may be increasing]] due to religious countries having higher birth rates in general.<ref name="CambridgeZuckerman2">{{cite book |last=Zuckerman |first=Phil |title=The Cambridge Companion to Atheism |date=2006 |isbn=978-1139001182 |editor1-last=Martin |editor1-first=Michael |pages=47–66 |chapter=3 - Atheism: Contemporary Numbers and Patterns |doi=10.1017/CCOL0521842700.004}}</ref>