Logan Paul is going head-to-head with Ryan Garcia ... but not in the ring -- the WWE Superstar's Prime Hydration just hit the boxer with a defamation lawsuit.
The Maverick aired his frustrations on social media just minutes ago ... claiming his drink company is "under attack" by false narratives being thrown around on social media -- and it's time to take action, with King Ryan being the first on his list.
"Today we begin to hold those accountable who’ve damaged our brand for attention while we correct the narrative," Paul said on Instagram.