The flying Dutchman placed second at Rome’s Stadio dei Marmi in Saturday’s penultimate leg of the competition, ensuring he cannot be caught when the riders travel to Doha in November.
Smolders, 37, guided his stallion Don VHP Z home in 52.43 seconds — a time bettered only by Sweden’s rising star Evelina Tovek on the day.
His nearest challenger, Lorenzo de Luca of Italy, could only finish in seventh.
It meant Smolders became the first rider in the competition’s history to wrap up the title before the season finale.
“Our goal was not to be the fastest today, but I wanted to keep clear,” he said. “It feels great to be champion.
“You see the previous winners, the horses and riders are exceptional. So to see my name on the trophy is special.
“It’s a big achievement for all my owners, our staff and everyone who works in our stable, from flat riders to the grooms. It’s also for them.”
Victorious in July’s Chantilly leg, Smolders has been the most consistent rider on the LGCT this season.
His reward is a place in the history books, alongside past winners such as Rolf-Goran Bengtsson, Luciana Diniz, Scott Brash, Edwina Tops Alexander and Ludo Philippaerts.