Weis Markets, Inc. is a Mid-Atlantic food retailer based in Sunbury, Pennsylvania, It currently operates 204 stores in Pennsylvania, Maryland, New York, New Jersey, West Virginia, Virginia, and Delaware.

Weis Markets was founded as Weis Pure Foods in 1912 in Sunbury, Pennsylvania by two brothers, Harry and Sigmund Weis. Their store has been noted as "revolutionary", as it did not operate on credit—sales were only for cash. At the time, similar stores operated on credit, allowing customers to build a tab that would be paid periodically. Cash sales were a sign of a growing working class earning steady paychecks—and they also helped lower prices by up to 25%.

The second Weis store opened in 1915 in Harrisburg, Pennsylvania. Harrisburg would remain an important market for Weis, helping to anchor the central Pennsylvania region that Weis would dominate for decades.

The Weis brothers expanded their chain rapidly, opening dozens of small, in-town grocery stores throughout central Pennsylvania. Their chain peaked at 115 stores in 15 central Pennsylvania counties by 1933. As the supermarket industry shifted to larger, self-service stores, Weis adapted the format of its stores. The company closed several corner grocery stores in Harrisburg in 1938, replacing them with their first self-service, consolidated supermarket. Over the next two decades, the company continued with this strategy, and it had consolidated all of its corner grocery stores into supermarkets, with 35 stores by 1955. In newspaper ads of the 1940s, Weis referred to its stores first as Weis Super Markets, then Weis Self-Service Markets, and finally Weis Markets.

In the 1950s and 1960s, Weis expanded its reach, first to York and then Lancaster by 1960. Weis expanded to Maryland in July 1967, opening its first non-Pennsylvania store in Hagerstown, followed by a store in Frederick in August Its first store in the Wilkes-Barre area opened in 1967. In November 1967, the company purchased the five-store Albany Public Markets chain based in Albany, New York in an all-cash transaction. It operated Albany Public Markets as a subsidiary, keeping the company's management team intact. Weis closed its Albany Public Markets chain in October 1986, leasing the nine stores to Grand Union.

Weis also expanded to western Pennsylvania, opening stores as far west as Altoona, Everett, and Philipsburg, and expanded throughout northeastern Pennsylvania. The company purchased two regional chains in the Poconos and Lehigh Valley region: Mr. Z's, a 14-store chain of IGA supermarkets, in 1992, and King's, a six-store chain based in Hamburg, in 1994. Mr. Z's and King's were operated under separate banners for years before all stores were re-branded as Weis.

Weis's expansion into the Baltimore, Maryland market was successful, but its expansions into the Washington, D.C. market were less successful. Weis opened stores in suburban Washington, D.C. and northern Virginia before retreating from that market, first closing most of its stores in Montgomery County, Maryland, and finally closing all stores in Virginia.

Weis also expanded into northern New Jersey, beginning with a store opened in Newton in 1992. A store that opened in Flanders closed in 2002, two years after its opening. Weis re-entered the Flanders market in 2014, in a former A&P store adjacent to the location of its first Flanders store.

In 2009, Weis expanded into the Southern Tier of New York with the acquisition of the 11-store Giant Markets chain. Weis closed one former Giant Market in Binghamton in 2012, along with two others in 2014. Eight former Giant Markets continue to operate.

Eastern expansion continued in 2012 as Weis acquired three former Genuardi's stores from Safeway, in the Philadelphia suburbs of Conshohocken, Doylestown and Norristown, on June 16. A former Superfresh store in Towson, Maryland, opened as a Weis in 2012. Weis entered central New Jersey with the purchase of a former Pathmark store in Hillsborough in August 2013. In November 2013, Weis opened its closest store to Philadelphia after acquiring a former Pathmark store in Huntingdon Valley, Pennsylvania. In July 2015, Weis purchased the location and assets of Nell's Shur-fine Market from C&S Wholesale Grocers in Penn Township, York County, Pennsylvania and followed that up in October 2016 with the purchase of a second Nell's location in East Berlin, Pennsylvania.

In May 2016, Weis Markets announced the purchase of five stores from Mars in Baltimore County, Maryland after that chain announced it was closing all its stores. In July 2016, it was announced that Weis Markets entered into a purchase agreement with Ahold and Delhaize Group for 38 Food Lion locations in Delaware, Maryland and Virginia as part of the divestiture of stores to gain clearance from the Federal Trade Commission for the impending Ahold/Delhaize merger. On October 5, 2016, Weis announced the purchase of Nell's Shur-fine Market in East Berlin, PA from C&S Wholesale Grocers. The company completed the acquisition and conversion of the 44 stores in early November 2016.

On March 9, 2017, Weis Markets opened a 65,000-square-foot (6,039 m) store in Hampden Township, Pennsylvania that features a pub, ice cream parlor, expanded takeout food selection, a drive-thru pharmacy, and a beer cafe selling 900 varieties of beer and 500 varieties of wine.

Robert F. Weis, the son of founder Harry Weis, joined the company in 1946 after serving in the U.S. Army Air Force. Early in his career, he worked in various positions including operations, distribution, marketing, procurement, human resources, real estate and store construction. Ultimately, Weis would oversee the company’s finances, real estate and store construction while working with his cousin Sigfried Weis, who became company President after the death of Harry Weis in 1962. When Sigfried Weis retired in 1994, Robert Weis became company chairman, a position he held until the spring of 2015 when he became Chairman Emeritus. Weis's son Jonathan, who was CEO at the time, succeeded him as Chairman. Robert Weis died on October 19, 2015.

The Weis supermarket located in Park Hills Plaza along U.S. Route 220 in Altoona, Pennsylvania was the subject of a key 1960s United States Supreme Court case concerning the "public forum doctrine." The Court held that a union picket in the supermarket parcel pickup area and parking lot was permissible because the "shopping center here is clearly the functional equivalent to the business district" of a city. At the time of the picketing, the Weis store was located in Logan Valley Mall, the Park Hills Plaza was not built until the mid 1970s, at which time Weis move across U.S. Route 220 to its current location.

In addition to the Weis Markets banner, the company once operated supermarkets under the King's and Mr. Z's banners. Those two banners were centered primarily in the Lehigh Valley and the Poconos, respectively, and were acquired in mid-1990s acquisitions. Since their acquisitions, these stores have been remodeled or replaced. In 2009, they were rebranded to the Weis banner, as was its Cressler's store in Shippensburg. In 2011, it converted its three Scot's Lo-Cost stores, located in Montoursville, Mill Hall and Coal Township, to the Weis banner.

Weis operates some stores as Save-a-Lot under license from SuperValu. At one time, the company operated a few stores as Big-Top Market, but as of 2006, no more stores exist under this banner.

Weis faces significant competition from various food retail formats, including conventional retailers, mass merchant retailers, discount retailers, drug stores, convenience stores, Walmart and dollar stores. Weis's chief competition comes in its traditional home base of central Pennsylvania. Giant (Carlisle), a supermarket chain owned by Ahold, began aggressive expansion during the 1990s, building large stores with expanded selections. Giant has remained the market leader throughout central and northeastern Pennsylvania.

Weis also faces tough competition in Lancaster County, Pennsylvania from Stauffer's of Kissel Hill.

In Maryland, Weis competes with Walmart, Acme, Giant Eagle, Food Lion, Harris Teeter, Safeway, ShopRite and Giant (Landover).

In New Jersey, Weis's chief competition includes ShopRite and Stop & Shop.

In New York, Weis's competition includes Price Chopper and Wegmans.

In 2011, it sold or closed its remaining Superpetz units, a move that is expected to enhance the company's overall profitability.

Weis Markets sells a variety of house brands under the following private brand labels:

Weis Markets is one of the supermarkets in Pennsylvania able to sell beer and wine in in-store cafés at some of its locations. In Pennsylvania, grocery stores cannot sell beer unless they operate a café. Weis Markets sells beer and wine at 52 Pennsylvania locations. In June 2016, PA Governor Tom Wolf signed Act 39 law permitting the sale of wine in licensed supermarket beer cafes.