Defence and aerospace group EADS has won a contract worth an estimated $2.27bn (£1.4bn) to help Saudi Arabia improve its border security.
The five-year deal will expand on the pan-European firm's existing contract with the Saudis to improve security along its border with Iraq.
The new deal covers all of Saudi Arabia's other land and sea boundaries.
EADS will provide everything from new radar stations to camera systems and reconnaissance aircraft.
Analysts said the Saudi government is particularly determined to strengthen its border with southern neighbour Yemen, which it blames as the main source of smuggled weapons used by militants.
"You want to increase the ability of the border guards to achieve their goals," Saudi Interior Ministry spokesman Mansour al-Turki told the AP news agency.
"It's not enough to rely on traditional technology."
EADS is said to have beaten France's Thales, UK firm BAE Systems, and US group Raytheon to win the contract.
Saudi Arabia has the world's ninth largest defence budget, spending $38.2bn last year, according to the respected Stockholm International Peace Research Institute.