The benchmark price of North America's main oil blend lost more than three per cent to change hands below $37 US a barrel on Monday, dragging the Canadian dollar below the 72-cent US level in the process.
West Texas Intermediate was going for $36.80 a barrel on Monday, down 3.4 per cent on the first trading day after a mini-rally last week.
The catalyst for the sell-off was a report that Iran intends to increase exports by 500,000 barrels per day once economic sanctions are removed. That would only add to excess global supplies that have helped depress oil prices.
Currently, the world is pumping out more than a million barrels per day of oil more than it needs to meet global supply. That's keeping prices low as it's a buyer's market.
The bleakness in oil has been bad news for Canada's dollar, which is closely tied to the commodity's value. The loonie was down more than a third of a cent at 71.93 cents US on Monday.
The Toronto Stock Exchange was closed for its Boxing Day holiday. But U.S. markets were open. The Dow Jones industrial average was down 23 points to 17,528.