Emmaus (/ɛˈmeɪ.əs/ em-AY-əs) is a borough in Lehigh County, Pennsylvania, United States. As of the 2020 U.S. census, it had a population of 11,652. Emmaus is located in the Lehigh Valley, the third-largest metropolitan area in Pennsylvania and 68th-largest metropolitan area in the nation.

In 2007 and again in 2009, Emmaus was listed as one of the top 100 "Best Places to Live" in the United States by Money magazine.

Emmaus is located 5 miles (8.0 km) south of Allentown, 53.4 miles (85.9 km) north of Philadelphia, and 91.6 miles (147.4 km) west of New York City.

Emmaus was settled in the early 1700s during the colonial era by German Protestants of the Lutheran and Reformed faiths who were fleeing religious persecution in Europe. Its earliest German settlers were primarily farmers.

In 1741, the land on which present-day Emmaus is located was donated to the Moravian Church by Sebastian Heinrich Knauss and Jacob Ehrenhardt for the purpose of creating a closed faith-based village. The village was originally named Salzburg. At the time of its founding in 1759, Emmaus was one of four leading Moravian communities in the Thirteen Colonies; Bethlehem, Lititz, and Nazareth, each in Pennsylvania, were the three others.

Two years later, in 1761, Moravian Bishop August Gottlieb Spangenberg announced the town's new name would be Emmaus, saying "Now here we build a village small; toward its completion we give all. Here, too, our hearts within shall flame; Emmaus then shall be its name." For approximately 100 years, until the mid-19th century, Emmaus was a closed community of the Moravian Church. Emmaus was named for the Biblical village of Emmaus, where, according to the Bible's Gospel of Luke, Jesus was seen by his disciples Luke and Cleopas in what is known as his Road to Emmaus appearance following his crucifixion and resurrection.

Three historic Emmaus residential structures built during the 18th and early 19th centuries, each still standing, have been added to the National Register of Historic Places. Shelter House, constructed in 1734 by Pennsylvania Dutch settlers, is the oldest building structure in Emmaus and the oldest continuously occupied structure in the Lehigh Valley. The 1803 House was built in 1803 in Emmaus by Revolutionary patriot militia member Jacob Ehrenhardt, Jr., son of one of the founders of Emmaus. Kemmerer House, built between 1840 and 1950, is a farmstead house in Emmaus.

From its founding in 1759 until 1830, the settlement's name was spelled "Emmaus." From 1830 until 1938, however, the community used the Pennsylvania Dutch spelling of the name, "Emaus," with a macron line above the "m" to indicate a double letter. As English began emerging as the prevalent language in Pennsylvania, however, the line often was often omitted, leading to confusion about the correct spelling. In 1938, the local Rotary Club circulated petitions in support of changing the spelling to "Emmaus," and its spelling was changed to match the English version of the Bible's King James Version. Despite the 1938 spelling change, a major borough thoroughfare, Emaus Avenue, continues to retain the pre-1938 spelling.