Today's protests, which were called mostly via social media by a variety of groups, are seen as a barometer of popular discontent with President Dilma Rousseff. Her second term in office has been shaken by a snowballing corruption scandal involving politicians from her Workers' Party, as well as a spluttering economy, spiraling currency and rising inflation.
Thousands of people brandishing green and yellow Brazilian flags streamed onto Rio's Copacabana Beach, and smaller demonstrations were under way in the Amazonian city of Belem and the central city of Belo Horizonte.
Rousseff's popularity ratings are at historic lows.