Citizens of all Western nations need a visa to enter. Holders of West African passports do not require a visa.
As of 2013, visas for Mauritania are no longer available at on arrival at land borders, so overland travelers have to arrange them in eg. Rabat. Single entry visa fee is 62,5 EUR, double entry is 125 EUR. Two passport-size photos are required, as well as a copy of the information pages of your passport. Visas are available on the next day for people of most nationalities. As of January 2012 this is true for Americans as well, although it is advisable to check that there have been no recent issues with long waits, so your travel plans are not interfered with.
If you are coming up from Senegal, you can also arrange the visa at the Mauritanian embassy in Dakar. Unlike Rabat, there is never a queue so you can show up any time so long as you have two photos and a photocopy of the information pages of your passport. They quote a turnover time of three days but usually it takes only one.
Visas are also available at the Mauritanian embassy in Banjul, Gambia. However, when I went there they said they could only issue transit visas or multiple entry, not single entry. I do not know if this was standard practice or just an attempt to trick me into buying the more expensive option. Do it in Dakar unless you cannot spare any time there.
For most people there are no vaccinations required in Mauritania. Only ones coming from yellow fever endemic zones are required to present a vaccination certificate.
From late May 2014 it is possible to obtain visa at the airport in Nouakchott the price for both Polish and British citizens was €50 each. For tourist purposes, a letter of invitation is not needed. Certain hotels can nevertheless issue a letter of invitation. It is advised to consult this with a Mauritanian Embassy, as the rules seem to change often.
Nouakchott International Airport IATA: NKC ICAO: GQNN is the base for Mauritanian Airlines (http://www.mai.mr/), which flies to, Dakar, Casablanca and ZOUERATT. It also receives flights from Algiers on Air Algérie (http://www.airalgerie.dz/...) and from Paris on Air France (http://www.airfrance.com/...) . Alternatively you can take a charter flight, which costs around €400.From July/August 2012 Iberia are launching a route from Noukchott to Madrid via Las Palmas in the Canaries. Fares from Mauri to LP seem to be hovering around 200 Euros. On November 16th, 2012 Turkish Airlines (http://turkishairlines.com) will add Nouakchott, to its network by extending its current Dakar service to the Mauritanian capital. Three direct flights per week will operate from Istanbul Atatürk International Airport, on Tuesdays, Thursdays and Sundays. Introductory round trip fares are available from Istanbul to Nouakchott with the prices starting from 299 Euros.
By Bus/Bush Taxi
From Morocco: Supratours runs a nightly bus to the border at Gargarate. It departs from the Dakhla waterfront at 23:59 and arrives at the frontier at 05:30 for 150 Dh.
It is also possible to get to the border by hitching with overlanders from Dakhla most can be picked up from Camping Moussafir just north of Dakhla or from the Mauritanian embassy in Rabat, or by paying for passage with Mauritanian traders. These can be found opposite the first police checkpoint north of Dakhla. The going rate is currently 250-380Dhs negotiable; the ride should be started rather early and takes most of the day. Cars with experienced drivers can be organized from Hotel Sahara the budget one. This costs around 250Dhs per person. Be careful to avoid a driver with an obvious facial pigmentation disorder. He has been known to behave aggressively towards passengers.Bear in mind that the border crossing is closed overnight.
From Senegal: Bush taxis can be taken from Dakar 6,000 CFA and St Louis 2,000 CFA amongst others to Rosso, where a ferry makes the trip across the Senegal river, and further bush taxis can be taken to Nouakchott about 2,000 UM. Be careful of bush taxis offering deals that seem too good to be true. They may be illegal taxis and could prove to be a dangerous means of transportation. There will most likely be a number of drivers waiting. Ask around and find out the going rate. Other crossing points from Senegal include the Diama dam just north of St Louis, public transport also operates on this route.
When you get to Rosso you will be told innumerate lies. You will be told that CFA cannot be changed on the other side of the river, that the next free ferry is two hours away and you should hire a boat, that you should arrange onward transport Senegal side for a better deal etc etc. None of this is true. Admittedly the banks will not change CFA but the shops will and at a better rate than the guys hanging around the ferry. The ferry goes back and fourth non stop. You do not need any help at customs, if someone tries to come on the ferry with you explain politely that you do not need any help and have no intention of giving them any money.
From Mali: Pickup trucks leave Kayes for Selibaby daily. It is also possible to enter at Nema, and across the southern border at several points.
Mauritania has open road borders with Western Sahara, Mali and Senegal. These borders are open to crossing by private motor vehicle or bicycle.
The road from The Western Sahara/Morocco enters the country near Nouadhibou. The road is paved all the way to the Moroccan border post in Fort Guerguarat, where one has to traverse about 7 kilometers of twisting, stony, but straightforward pistes to reach the Mauritanian border, where the tarred road begins again. Although the driving is simple, care should be taken not to leave the well worn pistes between the two border posts, because the area is a mine field. This danger is still present once you reach the tar on the Mauritanian side, and the area is not considered mine-free until you pass the railway line.
The crossing formalities are straightforward. Transit visas - valid for 3 days - can no longer be bought at the border, although this may change again. There is a bureau de change at the border, and a vehicle insurance office and numerous hopeful guides for making the old desert crossing down to the capital.
There are numerous pistes running across the Mauritanian border from Mali. These used to be the de facto route between the two countries, however there now exists a new tar road connecting Nara in Mali to Ayoun al Atrous in Mauritania. The border formalities in Mali are completed at various buildings around Nara town local children will lead you to the police or customs for a small present. The Mauritanian formalities are conducted at a string of road-blocks along the border road.
An alternative land route which goes direct from Mauritania to Timbuktu, Mali is to travel the road Southeast from Néma, which is at the end of a good tarred road from Nouakchott. This dirt road continues to Bassekounou before crossing the border near Léré, Mali where it improves to a good dirt road to Niafunké and on to Timbuktu.