The wrestler-turned-actor could charge advertisers more than $1m (£790,000) per post last year, according to the social media marketing firm Hopper HQ.
The Fast and Furious star knocked make-up entrepreneur Kylie Jenner off the top spot.
She has 182 million Instagram followers, while he has 187 million.
UK-based company Hopper HQ, which runs social media accounts on behalf of companies and individuals, published its first Instagram rich list in 2017.
The rankings and cost per post were arrived at after speaking with so-called social media "influencers" themselves, along with brands and marketing companies, and using publicly available pricing information to estimate how much each account could charge.
However, marketers tend to be secretive about how much they pay, or the posts may be part of a wider deal - as is often the case with A-list celebrities or sports stars - so the exact amounts are not known.
Other high value personalities on its list for 2019 included footballer Cristiano Ronaldo, who was worth $889,000 per post, and socialite Kim Kardashian West, who could charge $858,000.
Earlier this year, Dwayne "The Rock" Johnson was crowned by Forbes as the highest-paid actor in the world, having earned nearly $90m last year before tax.
Outside of his film work, the action star has a major commercial partnership with Under Armour, the US sports brand he signed with in 2016.
He has also been sponsored by tech giant Apple and the Norwegian bottled water brand Voss, in which he holds a stake.
However, his current list of endorsement deals on Instagram appears surprisingly short.
Scrolling through his feed, aside from selfies of the muscle-bound actor working out, most of The Rock's recent posts promote his own Tequila brand, Teremana.
Other than that, his promotional posts are largely for new episodes of The Titans, an NBC TV series which he hosts, or films in which he stars, such as upcoming DC Comics feature Black Adam.