WWE Selling Dirt From Undertaker's Wrestlemania Match, 'Demand Is Strong!'

Wanna own real live dirt The Undertaker used to bury A.J. Styles at Wrestlemania 36???

Better act fast because the WWE has collected the soil and put it up for sale -- and we're told it's already in super-high demand!!

If ya missed it ... 55-year-old Undertaker beat Styles in an epic "Boneyard Match" at Mania back on April 4 -- which featured the two wrestling stars fighting it out in a cemetery.

Now, to commemorate the tilt, WWE is selling real dirt from the night ... and the piece is actually pretty sick.

The memorabilia features a plaque with photos from the evening as well as a capsule full of the historic Earth that Styles was ultimately buried under.

WWE is listing the items for $74.99 a pop ... and is limiting quantities to just 536 total.

One source tells us ... "Demand is strong and it's already a top-selling item" on the official WWE online shop.

Of course, while it is just dirt ... WWE mementos tend to age pretty well -- some of the game-used items from iconic wrestlers in the past have sold for thousands!!