Benchmark U.S. crude fell by $1.96 to $96.52 per barrel in New York while Brent crude lost 98 cents to $112.20 per barrel in London.
The prices for both declined after voters in France and Greece rejected incumbent leaders that supported austerity measures to fix the region's economy, where unemployment and recession are spreading.
Analysts warned that the election results could derail the eurozone's plan for recovery. That could further disrupt an economy that consumes 18 percent of the world's oil.
In the U.S., retail gasoline fell 2.5 cents over the weekend to a national average of $3.777 per gallon.
