According to Sussex Police, Clayton McCalman left HMP Ford between 5am and midday on Monday (November 2), and his 'direction of travel is unknown'.
The 32-year-old is heavily linked to the London area, police said, and anyone who sees him is asked not to approach him 'but to dial 999 immediately'.
A police spokesperson added: "If you have any information about where he could be, you can report it online or call 101, quoting serial 0607 of 02/11.
"You can also contact the independent charity Crimestoppers anonymously on 0800 555 111 or report it online."
A message from the Editor, Gary Shipton:
In order for us to continue to provide high quality and trusted local news, I am asking you to please purchase a copy of our newspapers.
With the coronavirus lockdown having a major impact on many of our local valued advertisers - and consequently the advertising that we receive - we are more reliant than ever on you helping us to provide you with news and information by buying a copy of our newspapers.
Our journalists are highly trained and our content is independently regulated by IPSO to some of the most rigorous standards in the world. But being your eyes and ears comes at a price. So we need your support more than ever to buy our newspapers during this crisis.
Stay safe, and best wishes.