The M266 is a Mercedes-Benz inline-4 engine manufactured in Stuttgart and is used solely in vehicles like the A-class and B-class. The most powerful engine in the family is the 2.0 turbo, found in the Mercedes-Benz B200 Turbo.
| Engine | 1.5 | 1.7 | 2.0 | 2.0 turbo |
| Engine code | M266.920 | M266.940 | M266.960 | M266.980 |
| Capacity | 1498 cc | 1699 cc | 2034 cc | 2034 cc |
| Valvetrain | 8-valve SOHC | 8-valve SOHC | 8-valve SOHC | 8-valve SOHC |
| Head | Aluminium alloy | Aluminium alloy | Aluminium alloy | Aluminium alloy |
| Block | Aluminium alloy | Aluminium alloy | Aluminium alloy | Aluminium alloy |
| Bore × Stroke | 83 x 69.2 | 83 x 78.5 | 83 x 94 | 83 x 94 |
| Power | 70 kW/95 ps | 85 kW/116 ps | 100 kW/136 ps | 142 kW/193 ps @ 5,000 rpm |
| Torque | | | | 280 Nm @ 1800-4850 rpm |
| Induction | Naturally aspirated | Naturally aspirated | Naturally aspirated | Turbocharged |