No country owns Antarctica so there’s no visa required; however, the countries that have signed the Environment Protection Protocol to the Antarctic Treaty require that visitors need to obtain permission prior to arrival (often done through tour operators). Visitors to Antarctica are increasing steadily since 2011 and thankfully there are still no physical hotels to stay in or restaurants to eat at.
This is because most tourists arrive via cruise ships and sleep and eat on board and these tourist only venture out on excursion during the day. There are also no permanent residents in Antarctica. Most of the people who stay there are scientists doing research and research stations in Antarctica have supplies provided by their local government.