Big-box retailers aren’t selling CBD yet, but they’re busy getting ready for the day when they can.

The Post has learned that top executives at major chains such as Walmart and Target have been quietly meeting with makers of drinks, gummy bears, topical creams and oils that are infused with cannabidiol, or CBD.

CBD is an ingredient in marijuana plants that doesn’t get you high, but is said to relieve pain as well as stress symptoms including anxiety and insomnia.

The chains, which also include big supermarkets such as Kroger and Safeway, are requesting samples of CBD products, along with lab results and pricing information, manufacturers said.

That’s despite the fact that the Food and Drug Administration said in December that it’s illegal to spike food and beverages with CBD or THC — the pot ingredient that does get you high — or to transport them over state lines.

“We are flying around the country, talking to all the big guys at their headquarters,” said Christian Graversen, brand manager of California-based CBDfx, a 6-year-old company that makes more than 50 CBD-infused products including a $10 package of eight gummy bears.

“We are going multiple times to the same companies, meeting with their senior buyers, legal departments and merchandising executives,” Graversen added.

Major retailers are angling for a piece of the exploding CBD industry, which is expected to more than double to $2.1 billion by next year as consumers pay premium prices for products to treat maladies ranging from arthritis to ADHD.

Up to now, the lion’s share of the CBD bonanza has been going to mom-and-pop shops. But a few bigger chains, including Walgreens, CVS and GNC, have begun selling CBD-infused topical creams that treat wrinkles and pain in states where they’re allowed, including New York.

“We do not have plans to carry CBD products at this time,” Walmart said in a statement, declining to elaborate on its CBD strategy.

“Like many companies, we know there is consumer interest in CBD products, and the conversation is evolving quickly,” a Target spokesperson said. “We’re following the discussion, but currently don’t have any immediate plans to carry them.”

Nevertheless, both chains are not only doing due diligence on CBD but also hatching plans for how to sell it, sources said.

“The major retailers are [designing] shelves, laying out space where CBD products will sit in their stores, but they aren’t buying any product yet,” said Michael Kirban, chief executive of Vita Coco.

The coconut water brand is planning to roll out a version of its drinks this summer infused with hemp, a non-psychoactive component of marijuana that last December got removed from a list of illegal substances under federal law with the signing of the US Farm Bill.

But the rollout will likely be limited to smaller chains and stores, Kirban said. Bigger retailers are waiting on a permanent FDA ruling on marijuana-based products, which is not expected until the end of this year at the earliest.