Almost everyone arrives by air at Juba International Airport (JUB). Direct flights operate from Nairobi (Kenya Airways), Entebbe (Uganda Airlines), Addis Ababa (Ethiopian Airlines), and Cairo. Nairobi is the most common routing hub.
The one paved road into South Sudan crosses from Uganda at Nimule, then follows the 192km Nimule–Juba highway to the capital — the only sealed international road in the country. The crossing is possible in a 4x4, and the road is generally fine in the dry season. The border at Nimule is straightforward but expect delays.
All other overland crossings are difficult, unpaved, and should be treated as serious expeditions. The border with Sudan is effectively closed. Crossings from the Democratic Republic of Congo, Central African Republic, and Ethiopia exist on maps but require local knowledge, good vehicles, and ideally current local contacts.
Visas are required by all nationalities. South Sudan has an e-visa system — apply online before travel, allow a week, and expect to pay around $120 (more for US citizens). Your passport must be valid for at least 6 months. Yellow fever vaccination is mandatory and will be checked at entry. Bring your vaccination certificate.
If you are staying longer than 3 days, you are required to register with the Department of Immigration and Aliens Control at the Ministry of Interior in Juba.