The new service is called BMW Direct, and its online parts service joins a line-up of accessories and car-care products that have been on sale since March.
The 'shopfront' is to be handled by BMW, while the order processing is being dealt with by BMW Park Lane.
BMW's first venture into e-commerce will, says BMW allow it "to reach those customers not accustomed to visiting a BMW dealer regularly".
"eBay UK is home to over 100 leading brands who realise the added value an eBay shop brings, whether they are already selling online or not," says Angus McCarey, UK retail director of eBay. "There are over 600,000 searches for BMW every month on eBay and BMW will now be able to access this existing, yet untapped customer base, while increasing its reach to the millions of other consumers who buy and sell on the site."
Those customers won't, as yet, be able to buy whole cars direct from BMW via eBay, however - and the car maker says it has to plans to sell its vehicles in this way.