The Michelin-starred pub and restaurant, which has been run by chef-patron Andrew Pern for the past 25 years, was 'reduced to ashes' last week as a result of the blaze.
Police investigating the fire are appealing for witnesses and information about the incident.
In a statement, North Yorkshire police said: “Following an examination of the scene by police crime scene investigators and fire investigation officers, it is now believed that the fire was started deliberately.
“A number of groups of people were in the area around the time of the fire, and police are urging anyone with information about the incident to contact them.”
It appealed for those with information to contact the force on 101, quoting reference 12210248468; or to call Crimestoppers anonymously on 0800 555111 or go to their website.
Emergency services were called to the fire at the Star Inn, Harome, just before 10.15pm on Wednesday 24 November 2021.
At its height, 45 firefighters tackled the blaze, with all occupants managing to leave the restaurant safely.
Posting a video of firefighters tackling the blaze on social media last week, Pern wrote: "It's been a long night so far…..I'm afraid we won't be open for a while as we are reduced to ashes with The Star on fire and still burning."
The Star at Harome is one of the UK’s best-loved gastropubs known for its low-beamed wooden ceilings and traditional interior. It currently sites at number two in the Estrella Damm Top 50 Gastropubs list.