The South Korean won ended onshore trade at 1,112.1, down 1.2 percent from Friday's close at 1,098.7 and capped the worst daily percentage fall since late October last year.
During Monday's session it touched 1,112.6, the lowest level against the dollar since Dec. 9.
The Korea Composite Stock Price Index (KOSPI) closed down 1 percent at a 1-1/2 week closing low of 1,992.82 points - it was also the sharpest daily fall in nearly two months on Monday.
Selling by foreigners and institutions dented the benchmark, dumping 64.6 billion won ($58.10 million) and 176.2 billion won worth of local shares, respectively.