The new Mazda 3 will cost from £13,500 when it goes on sale in May.
Buyers initially have a choice of three petrol and three diesel engines.
Petrol engines are a 104bhp 1.6-litre, a 147bhp 2.0-litre, or a 149bhp 2.0-litre. A 256bhp 2.3-litre unit will be launched in the hot MPS model later this year.
Diesel choices are a 107bhp 1.6-litre, 147bhp 2.2-litre and 182bhp 2.2-litre.
Fuel economy has been improved by up to 16 per cent and carbon dioxide emissions reduced by up to 19 per cent.
This is aided by the new Mazda 3's more aerodynamic shape, retuned engines and lowered weight. Mazda has also introduced stop-start 'i-stop' technology on the 2.0-litre Sport model.