All trading on the São Paulo Stock Exchange was halted for half an hour. The halt was triggered automatically after the benchmark index fell by more than 10 percent during the day.
At closing, it was down 14 percent.
An analyst who spoke to Bloomberg describes the development as a "tsunami hitting all Brazilian assets" and says uncertainty is likely to persist for several weeks.
It’s not just the stock market that’s taking a beating. Brazil’s currency, the real, lost around 10 percent against the US dollar on Monday.
The sharp declines came after the market had expected right-wing candidate Flávio Bolsonaro, who won the first round of the election, to emerge victorious.
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