Since September, Qanon content had been down-ranked by Facebook’s algorithm, but not removed.
The social media site says it is now “prohibiting anyone on our platform from running ads that praise, support or represent militarized social movements and QAnon."
Facebook will also direct users to “credible” child safety resources should they come across Qanon hashtags.
That is because QAnon uses phrases like “#savethechildren” to recruit and organise, due to its conspiratorial ideology that President Trump is secretly working to save the world from a satanic cult of paedophiles and cannibals.
“In addition, content about QAnon and child safety is eligible for fact checking through our third-party fact-checking program," Facebook said.
“Content that is debunked will be reduced in News Feed and filtered from Explore and hashtags on Instagram will receive a label (so that people who see it, try to share it or already have, will see more context), and it will be rejected as an ad.”
The FBI has deemed QAnon a threat, and considers the theory a strong motivator for extremist violence.
In one example from earlier this year, a woman filmed herself on a high-speed car journey carrying several knives to “take out” Joe Biden.
In August, Facebook took down over 790 groups, 100 Pages and 1,500 ads tied to QAnon.
Additional restrictions were placed on over 1,950 Groups and 440 Pages on Facebook, as well as over 10,000 Instagram accounts.
Many other social media platforms have also restricted QAnon content. Twitter shut down thousands of accounts associated with the movement, saying it had the potential to inspire or motivate acts of violence.
More than a third of Republicans believe the QAnon conspiracy that Donald Trump is waging a secret war against a shadowy cabal of paedophile cannibals is "mostly true".
In the United Kingdom, QAnon believers are also a part of the anti-mask movement, which recently held a protest in Trafalgar Square.
At the core of the QAnon movement is the theory that an anonymous government insider called “Q” is posting secret codes on the 4chan message board /pol/ about an upcoming “storm” – a great change they believe will happen under the Trump presidency.
However, security researchers examining the “codes” have said that they are “not actual codes, just random typing”, based on an analysis of the letters and numbers used in the communications.
When asked about the conspiracy theory, Mr Trump said he was willing to put himself “out there” to help.
The Biden campaign said Mr Trump's response to QAnon was another example of the president "giving voice to violence".