Turkey's main share index closed 10.47% down following investor concerns over the escalation of anti-government protests over the weekend.
The Borsa Istanbul 100 index tumbled as investors feared the demonstrations could hit the economy, and the Turkish lira fell to its lowest in 16 months.
Demonstrators nationwide clashed with police after water canons and tear gas were used to control crowds. The protests were originally sparked by plans to build on an park in Istanbul.
As well as sharp falls in the stock market, there was also a big rise in the cost of insuring Turkey's debt against default on Monday.
The central bank cut its main interest rates by 50 basis points last month in a bid to stimulate the faltering economy.
Turkey's economic growth was just 2.2% in 2012 after rising more than 8% in both 2010 and 2011.