Mazda does not supply a rated towing capacity for the Mazda3, probably for legal reasons. Some people say you can bolt/weld on a class 1 hitch, and speculate that it should be fine for towing 1000 lbs, but this is unofficial (see related links).
Previous answer, but the poster did not mention their source of information:
500 kg without brakes
900 kg with brakes
According to Mazda 3's own specs, the car has zero towing capacity. That is, Mazda does not recommend towing anything. Compare this with the Toyota Corolla, which has a 1500 pound capacity.
my 2006 1.6 Diesel saloon has a towing limit of 1300kg and a noseweight of 75kg. It has no trouble towing my 800kg caravan
3 hunnet
== ==
14.5 gallons
5qt
I have a 5.4 v8 F350 XLT (regular cab long bed) and it has 3:73 gears and I believe the towing capacity is 16,000 pounds.
about 7,000 pounds
2200Kg
Lizard Lick Towing - 2011 3-7 was released on: USA: 23 July 2012
The standard towing capacity of this 1996 Ford F-250 4x4 is 10,000 pounds. This is for the 7.5 Liter engine.
The towing capacity of a 6-cylinder Ford E-150 conversion van is 1,200 lbs. It also has a 3-speed automatic transmission and a 4.9 liter engine.