The Legg Mason Tennis Classic, a staple of the late-summer sporting scene in the Washington area for more than four decades, is getting a dramatic makeover that will include a new title sponsor, stadium upgrades and shared billing with an existing tournament for rising women’s players.

The key development driving the changes is a new title sponsor in Citigroup, which will replace Baltimore-based Legg Mason after an 18-year association with the hard-court classic.

To be known as the Citi Open, the tournament will remain at Washington’s William H.G. FitzGerald Tennis Center in Rock Creek Park. But the venue will be expanded to include a new 2,500-seat show court and five new practice courts, with both projects targeted for completion by the start of this summer’s tournament on July 28.

Tournament director Jeff Newman called the multi-pronged initiative “a sustainability plan” for the event, which is one of 11 ATP 500-level tournaments in the United States. That classification guarantees sufficient prize money (nearly $1.7 million this summer) to lure many of the world’s top 20 players. Last year’s winner was Radek Stepanek of the Czech Republic, who defeated Gael Monfils of France in the final.

The women’s event, which had its debut last summer in College Park, is a few rungs below in terms of purse, status and drawing power, classified as an International event on the WTA calendar. Known as the Citi Open, it was won by Russia’s Nadia Petrova, who defeated Israel’s Shahar Peer for the title. Tournament officials hope to increase the purse for the women’s tournament (roughly $250,000 now) and its prestige and marquee value in the coming years.

The Citi sponsorship is a five-year deal.

Donald Dell, chairman and co-founder of the tournament, expressed his gratitude for Legg Mason’s support over the years — the longest-running title sponsor of a tennis event in North America.

This summer’s event will run from July 28 to Aug. 5; the men’s and women’s matches will be contested at the Rock Creek Park site.

The timing conflicts with the 2012 Summer Olympics in London, which will impact the men’s field in particular.

But top American Mardy Fish, currently ranked ninth in the world, is among those expected to compete in Washington. Former world No. 1 Lleyton Hewitt also is expected to take part.

From the fans’ perspective, the most significant changes will be the stadium upgrades. While the tournament boasts an impressive center court — with suites, large video scoreboards that display the replay of contested calls and lighting that enables matches to stretch beyond midnight if needed — the venue has lacked a suitable show court for its most popular matches not scheduled on center court.

That will be remedied with a 2,500-seat show court constructed just north of the stadium court, supplanting three existing practice courts. Elsewhere on the grounds, five new practice courts will be built to accommodate the needs of the men’s and women’s fields.

Construction is expected to start in May. There are no plans to expand or upgrade parking facilities on the grounds, which are owned by the National Park Service.

The tournament will continue to be owned by the Washington Tennis and Education Foundation, a charitable organization that provides tennis instruction and educational support for junior players in the area. In February, the WTEF broke ground on a $10 million tennis complex in Ward 7 to better serve the region’s youngsters.