Al-Attiyah, with Belgian co-driver Fabian Lurquin, had led overnight after taking his 50th career stage win and made no mistakes as he handed Dacia a first victory at their second attempt in the two-week event held entirely in Saudi Arabia. The 55-year-old Qatari also won in 2011, 2015, 2019, 2022 and 2023.
Ford's Nani Roma finished second, nine minutes and 42 seconds behind, and teammate Mattias Ekstrom was third after winning the final stage.
Last year's winner Yazeed Al-Rajhi of Saudi Arabia withdrew in the opening week after mechanical problems.
Benavides had earlier taken the motorcycle title after American Ricky Brabec lost his way and saw victory slip through his fingers.
The KTM rider, whose older brother Kevin won the Dakar in 2021 and 2023, came home second in the 105-km stage in Saudi Arabia's Red Sea port of Yanbu, with Honda's overnight leader Brabec 10th.
In a gruelling endurance event spanning two weeks and 8,000 km over rocky roads, through canyons and vast expanses of desert dunes, twice winner Brabec blew his chances with only a few kilometres remaining.
Spaniard Tosha Schareina finished third overall for Honda.
"From the start to the finish, I never stopped dreaming, I never stopped believing," said Benavides, who had trailed Brabec by three minutes and 20 seconds after Friday's penultimate stage.
"I said to all my people around, 'I don't know why, but I still feel it's possible, I still believe I can win and it's going to go my way.'
"In the last three kilometres, Ricky took a wrong piste and I took a good one... I just saw the opportunity and I took it."
American Skyler Howes was fourth overall for Honda, ahead of Australia's 2025 champion Daniel Sanders on a KTM.
Sanders crashed on stage 10 but refused to retire and raced on despite a suspected broken collarbone.