Canada's Janine Beckie scored the fastest goal in history as she netted within 20 seconds of the match against Australia.
In the very first match, Sweden women took on South African eves in which the Swedes scripted a narrow 1-0 win thanks to Nilla Fischer's early goal.
Hosts Brazil defeated China 3-0 thanks to goals from defender Monica, Andressa Alves and Cristiane. Former world player of the year Marta was the star attraction in this high voltage game.
Brazil are placed in Group E along side China, Sweden and South Africa. They take on Sweden on August 7.
In the another match, giants of women's football, USA defeated New Zealand courtesy goals from star footballer and world footballer of the year Carli Lloyd and Alex Morgan. The win helps USA to increase their unbeaten streak to 12 matches.
Some other results from the first of Rio Olympics 2016 are:
Germany 6-1 Zimbabwe
Canada 2-0 Australia
France 4-0 Colombia
Here are the current group standings: