According to the supermarket, the flesh is smooth and creamy, pale in colour and rich in flavour.
Usually reserved for top restaurants, the avocados are only available in December, and grown in Spain.
The fruit is apparently delicious deep-fried, and will be available for £2 in selected M&S stores throughout December.
Charlotte Curtis, M&S agronomist, said: “We’ve had the mini, the giant, ready-sliced and we’re now launching the holy grail of avocados – stoneless! This amazing fruit has been on our radar for a couple of years and we’re very excited to have finally been able to get hold of some for our customers to try.
“We know they will be in demand and we’ve only been able to get our hands on a limited amount so make sure you get them while you can!
“They’re perfect for snacking and lunchboxes as they can be eaten whole but can also be used for a beautiful garnish or in a salad. My top tip is to try them deep fried!”