The gelatine-free vanilla-flavored treats are priced at £1.50 a bag and are available instore nationwide.
Announcing the launch on Instagram, the company said: "Say hello to our FIRST EVER vegan marshmallow! A national food retailer first, our Plant Kitchen marshmallows are fluffy, delicious, and made without the gelatine. Pick up in-store now, and try in s'mores or rocky road.
'Soft and squishy'
According to the Mirror, M&S Product Developer Katy Patino said: "The key to the Marshmallows was making sure they are suitable for vegans with absolutely no compromise on the texture of flavor!
"We made sure each pack is full of the best soft and squishy marshmallows that give you a warm and fuzzy feeling inside when you pop them into your mouth – we can't wait to hear what customers think about them!"
Last year, Marks and Spencer scooped the Vegan-Friendly High-Street Retailer Award for its vegan logo which adorn its food and fashion items.
Plant Kitchen - includes more than 50 dishes including No Beef Burgers, Cauliflower Popcorn Bites, and coleslaw.
Earlier this year, No Chicken Kievs filled with garlic sauce, No Tuna & Sweetcorn Sandwich, No Duck Spring Rolls, and ToFish & Chips, among others, were added to the range.