Either a ship/boat or spacecraft/station would count, aircraft would also but I don’t think they have the staying power to qualify. What is the longest someone has been known to be in such a craft continuously without touching ground? Transfer between vessels is OK as well as extra vehicular activities such as swimming or spacewalking. I’m talking about time they left the ground to the time they came back to it.
The record for an airplane is an amazing two months by Robert Timm and John Cook. They flew a Cessna in circles over the desert near Las Vegas in 1958. Periodically they’d swoop down low and refuel from a chase car.
Jon Sandersalmost certainly holds the record for boats, having spent more than 658 days at sea during three continuous circumnavigations in 1986-1988.
I remember being told that historically some Tanka people never left their boats during their lifetime.
I would actually suspect that many sailors of the past spent far longer than 658 days at sea. During the Napoleonic Wars common seamen would often be placed on a ship and never touch shore for many many years. But these are the guys whose names are lost to history. The captains, officers and other trusted seaman would go to shore on a regular enough basis.
This seems doubtful to me. Currently the Sea Gypsies of Malaysia live on boats full time, but they do go to land as needed to get water, wood to repair their boat and other supplies as practically needed. To sustain oneself entirely at sea you’d need an infrastructure supporting it. The seamen stationed on the British Ships of the Line has that infrastructure, and they were kept there because if they let those people off the boat they often were not going to be coming back.
Also, some guys in the Napoleanic days spent their prison sentencesin old ships anchored at some harbor.
I came here to mention that. They also “changed oil” in some manner while flying.
In a related category some guy lived in cave for about a year by himself. He had topside communication but it was pretty limited (or in other words it was just to relate some basic info, not to have a nice long chat). Then, awhile later I think he did an even longer stint. And I think he was French.
Not quite what the OP was asking but still an interesting exercise in being “cut off” from the “normal” world for an extended period.
Didn’t L Ron Hubbard spend a few years at sea?
I may be misremembering.
Not the same duration as some of the examples already given, but American nuclear submarines operated on a system of gold and blue crews. The submarine would have two completely separate crews and they would rotate tours of duty. They would fly a crew and supplies out to a forward base (like Scotland) and the submarine would exchange crews and load up with supplies. The crew would then stay on station for a period of 70-80 days before returning for the next exchange. The crew that wasn’t on ship duty would get leave and train until it was their turn to exchange back on board.
That would be tough.
I thought it was at/in a volcano 
I’d say these unfortunate people, otherwise known as galley slaves, are the most likely candidates. They were literally chained to their ships for many years.
While it’s true that sailors in the age of discovery and after that spent many months, maybe years at sea, at one point the ship would reach land to replenish water supplies etc.
Man, that sounds stultifyingly boring. Pooping must have been unfun. They must have been close friends.
You may be thinking of the Tonka people. They never left their trucks, which were indestructible.
You might be thinking of the lego people, whose vehicle parts were light weight, modular, and for whom repairs were a snap.
Especially when you consider the second place record is 46 days. They broke that and then went on for another 18 days.
One hour after I broke the old record, I’d have been saying “Fuck it. Let’s land.”
This was my thought. The Brits would often impress sailors to serve on ships and so they were essentially captives/slaves…and so couldn’t be trusted to leave the ship. They probably spent a long time on board. However, I have no cite.
This.