The Mercedes-Benz GLS-Class (chassis code X166) debuted in late 2015 for the 2016 model year as the comprehensive facelift and rebranded version of the second-generation GL-Class. Adopting the S-Class suffixed moniker reinforced its status as the premier flagship SUV in the Mercedes line. It retained its spacious seven-passenger three-row cabin, standard AIRMATIC air suspension, and heavy towing capabilities.

The facelift introduced a bold front grille, revised LED headlights, updated taillights, and a refined interior featuring a tablet-style COMAND display. Engine offerings spanned the GLS 350 d with a 3.0-liter V6 turbodiesel, biturbo V6 and V8 gasoline models (GLS 400, GLS 500/550), and the top-spec Mercedes-AMG GLS 63 packing a 585-hp 5.5-liter twin-turbo V8. Transmissions were updated to the 9G-TRONIC nine-speed automatic on most variants.