Completion of the South Station tower in 2025 will deliver nearly 800,000 square feet of office space, the last major office project in Boston to break ground in the post-COVID era. Photo by Steve Adams | Banker & Tradesman Staff

South Station Tower’s first office tenant is a national law firm that will relocate from its Financial District offices next year in a landmark deal for Hines’ $870 million development.

Jones Day will occupy 41,000 square feet in the 51-story tower, which includes 22 stories of office space beneath the Ritz-Carlson Residences condominiums.

The firm will occupy the 23rd and 24th floors within the office section of the building, which includes the 12th through 34th floors, after signing a 15-year lease, developer Hines announced. The Washington, D.C.-based law firm opened its first Boston office in 2011 at its current location, 100 High St.

“Our new workspace will welcome clients, foster collaboration and community, reflect our belief that our best ideas thrive in an environment that encourages being together, and reinforce Jones Day’s Boston office as a premier destination for clients and top legal talent,” Boston Partner-in-Charge Colleen Laduzinski said in a statement.

The lease runs for 15 years, Hines announced. The tower built on air rights above the train station platforms includes approximately 680,000 square feet of office space and is scheduled to open next year.

The Collaborative Cos. began marketing the 166 luxury condos designed by Jeffrey Beers Interiors in late 2023, with prices starting at $1.3 million.