WS Development is a privately held, vertically integrated real estate owner-operator and developer headquartered in Chestnut Hill, Massachusetts. Founded in 1990, the company develops, owns, operates, and leases retail-led mixed-use properties across the United States. The firm manages over 300 properties totaling more than 25 million square feet of space, with an additional 10 million square feet under development. The company's portfolio includes retail, office, residential, hotel, lab/research, and entertainment properties, with particular concentration in urban mixed-use developments and lifestyle centers. WS Development operates with in-house capabilities spanning development, construction, leasing, property management, capital markets, design, and marketing. The portfolio is concentrated in the Northeast, particularly the Greater Boston area, where the company is developing Boston Seaport, one of the city's largest active projects encompassing 7.6 million square feet across 33 acres. Additional holdings span Florida, Illinois, Pennsylvania, and other East Coast markets. Major tenants include Amazon, which occupies over 1 million square feet across multiple Boston Seaport buildings, and Foundation Medicine. In November 2025, the company acquired Station Square, a 646,000-square-foot mixed-use district in Pittsburgh spanning 27.5 acres.