Brisbane is a large city with good transport system, so in the city you don't need to rent a car to get around. But if you like to visit outer suburbs or places outside the city such as Gold Coast or Sunshine coast, you're better off renting one.
Courtesy of Tourism Queensland
All the large companies are represnted in Brisbane:
NOTE: This website is written in British English, which is the English we use in Australia. You will find words like "traveller", "harbour" and "realise", and they are all correct in the language used in Australia.