TMZ is reporting that Blake Shelton has just declared war on In Touch -- suing the magazine over a cover insinuating he checked into rehab after his split from Miranda Lambert ... and he's looking for MILLIONS.

Shelton's beef is over a September 28th cover that featured a picture of Blake along with the headline, "Rehab for Blake ... He Finally Hits Rock Bottom."

In his lawsuit, filed in L.A. County Superior Court, Shelton says he's NOT in rehab and has no plans to go to rehab -- and he wants to set the record straight by suing In Touch's parent company, Bauer Media.

In fact, Blake calls BS on several specific lines from the article, including:

-- "Blake has hit rock bottom"
--  "His friends are terrified that he could end up dead at this rate"
-- "Blake's drinking and womanizing are what helped torpedo his 4-year marriage"
-- Mr. Shelton was "caught" by Ms. Lambert with "a bunch of naked women" in their home
-- "His close friends have talked about an intervention"

Blake wants AT LEAST $2 MILLION to make things right.

See the entire TMZ story HERE

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