The Wisconsin Evangelical Lutheran Synod (WELS) is a North American Confessional Lutheran denomination of Christianity. Characterized as theologically conservative, it was founded in 1850 in Milwaukee, Wisconsin. As of 2008, it had a baptized membership of over 389,364 in more than 1,290 congregations, with members in all 50 US states and 4 provinces of Canada. It is the third largest Lutheran denomination in the United States, following the Evangelical Lutheran Church in America (ELCA) and the Lutheran Church - Missouri Synod (LCMS).

WELS is in fellowship with the Evangelical Lutheran Synod (ELS), a smaller denomination based in south-central Minnesota, and is a member of the Confessional Evangelical Lutheran Conference (CELC), a worldwide organization of Lutheran church bodies.

WELS and ELS are independent Lutheran denominations and are not part of the ELCA, which is structured to have "synods" within the denomination. Thus, the term "synod" as used by the ELCA refers to middle level administrative districts in different regions of the United States (example: Illinois Synod of the ELCA), whereas in the case of WELS and ELS, "synod" refers to the entire church body.

Wisconsin (ⁱ/wɨsˈkɒnsɨn/) is a US state located in the north-central United States and is part of the Midwest and Great Lakes regions. It is bordered by Minnesota to the west, Iowa to the southwest, Illinois to the south, Lake Michigan to the east, Michigan to the northeast, and Lake Superior to the north. Wisconsin is the 23rd most extensive and the 20th most populous of the 50 United States. Wisconsin's capital is Madison, and its largest city is Milwaukee. The state is divided into 72 counties.

The word Wisconsin originates from the name given to the Wisconsin River by one of the Algonquian speaking American Indian groups living in the region at the time of European contact. French explorer Jacques Marquette was the first European to reach the Wisconsin River and record its name, arriving in 1673 and calling the river Meskousing in his journal. This spelling was later corrupted to Ouisconsin by other French explorers, and over time this version became the French name for both the Wisconsin River and the surrounding lands. English speakers anglicized the spelling to its modern form when they began to arrive in greater numbers during the early 19th century. The current spelling was made official by the legislature of Wisconsin Territory in 1845.

The Evangelical Lutheran Synod or ELS is a US-based Protestant Christian denomination based in Mankato, Minnesota. It describes itself as a conservative, Confessional Lutheran body.

There are approximately 19,945 baptized members in 142 established congregations and 12 mission churches. The current president is the Rev. John Moldstad, M.Div., S.T.M., who has been serving since 2002. Note that the ELS uses the term synod differently from the Evangelical Lutheran Church in America and is a separate denomination.

The Evangelical Lutheran Synod traces its history back to 1853 when the "Norwegian Synod" was organized in the Midwestern United States. They practiced "fellowship", a form of full communion, with the Lutheran Church - Missouri Synod (LCMS) during the 1850s and 1860s. In 1872, they along with the LCMS and the Wisconsin Evangelical Lutheran Synod (WELS) formed the Evangelical Lutheran Synodical Conference of North America.

In 1917, the Norwegian Synod merged with two other Norwegian Lutheran groups and formed the Norwegian Lutheran Church of America, later named the Evangelical Lutheran Church. This led to disagreement among members of the Norwegian Synod. The people who became the ELS had concerns regarding fellowship with those who did not share the same doctrine. The Norwegian Synod had taught that conversion and salvation were entirely the work of God without any cooperation from humans. The new merged church allowed that conversion depended in some degree on humans accepting God's grace. A group of people therefore gathered at Lime Creek Lutheran Church near Lake Mills, Iowa, in June 1918 and reorganized as the Norwegian Synod of the American Evangelical Lutheran Church (also known as "Little Norwegian" Synod) The name was later changed to the Evangelical Lutheran Synod in 1957.

 Martin Luther (help·info) (10 November 1483 – 18 February 1546) was a German monk, priest, professor of theology and iconic figure of the Protestant Reformation. He strongly disputed the claim that freedom from God's punishment for sin could be purchased with money. He confronted indulgence salesman Johann Tetzel with his Ninety-Five Theses in 1517. His refusal to retract all of his writings at the demand of Pope Leo X in 1520 and the Holy Roman Emperor Charles V at the Diet of Worms in 1521 resulted in his excommunication by the pope and condemnation as an outlaw by the Emperor.

Luther taught that salvation is not earned by good deeds but received only as a free gift of God's grace through faith in Jesus Christ as redeemer from sin. His theology challenged the authority of the Pope of the Roman Catholic Church by teaching that the Bible is the only source of divinely revealed knowledge and opposed sacerdotalism by considering all baptized Christians to be a holy priesthood. Those who identify with Luther's teachings are called Lutherans.