WASHINGTON — Reston, Virginia-based government IT contractor Science Applications International Corp. will acquire Chantilly-based Engility Holdings. It’ll create one of the largest government IT contractors in the country, with a combined revenue of $6.5 billion.

The all-stock deal is worth $2.5 billion, including the repayment of $900 million in Engility debt. The merger is expected to close by February, and has already been approved by the boards of both companies.

The merged company will retain the SAIC name and remain headquartered in Reston. SAIC CEO Tony Moraco will continue in his position, and the company will now have more than 23,000 employees.

“The highly complementary portfolios, combined with our similar cultures, operating models, and histories, make this transaction a compelling combination that enhances the value proposition for our customers, employees and shareholders,” said Moraco.

It merges Engility’s space and intelligence customers with SAIC’s engineering and enterprise IT customers, and gives the new company room to significantly grow its ties with government contracting.

It will make SAIC one of the largest independent technology integrators in government services.

SAIC will repay Engility’s outstanding debt with financing from Citigroup Global Markets.

Engility acquired fellow government IT contractor TASC in 2014 for $1.1 billion.