Updated May 2023
Border with Morocco open in both directions now.
Algerian border at Tindouf: tourists require permits from both countries
Atlantic Route visas 690 dirhams/1 day in Rabat or €55 all borders and airports.
The Nouadhibou-Nouakchott highway is secure with several checkpoints and roadhouses.

Money
Mauritanian ouguiya exchange rates; now about 41 to a euro. You can buy it black market at the Moroccan border post or in Morocco- RIM No Mans Land or officially at the border/airports.

Note that in 2018 the ouguiya lost a zero along with the introduction of new plastic notes (‘MRU’; right 50 oogs, about £1.20). Locals will still say ‘2000’ when they mean 200 in new money. Don’t get shafted!

Price and availability of fuel (per litre)
Nouadhibou –  Chami – Nouakchott – Akjoujt – Atar: UNL 43 / DZ 39 (TBC)
Chinguetti, Oudane and similar villages: ask locally (from drums)
Zouerat – Unl / Dz ~ 30
Bir Mog – Unl / Dz ~ 25 (pumps)
World fuel prices.

Some places on the N2 highway south of Nouadhibou try and charge up to 60 oogs for petrol from a drum, but Chami – less than 200km from the border and 270km from NKT has a regular station with another 13km south of town. All seem to run out of petrol from time to time so fill up when you can if you have a small range.

Costs
Moderate. Along with a new flag and new banknotes, in 2018 the resumption of inexpensive charter flights to Atar gave organised tourism (local agencies) a long-awaited shot in the arm. If you don’t want to join a group you can rent a Hilux crewcab and driver from €75 a day + fuel, and a cook for €15-20 a day + food.

Useful languages
French, Arabic (Hassaniya).

Visas
Visas are issued at airports and the Moroccan, Algerian, Senegalese (Rosso) and Mali (Gogui only) borders. In a bid to revive tourism, in 2017 the visa dropped to €55, plus an optional €10 to a border transiteur (‘fixer’). On your visa it ought to say €55. Go to the last post of this thread to read about recent visa experiences on the Atlantic Route. They will now try and trick you for parking fees at border posts. Ask if there is a place to park for free.

Visa in Rabat is nearly the same price (690 dh) as the border, but takes a day, so why bother unless you need multiple entry?
6, Rue Thami Lamdawar
Rabat-Souissi
N33°58.8′, W06°49.9′
email (+212) (537) 65 66 78
Apply Monday to Thursday 9-11am (queueing from 7am, some sleep in their cars), and collect same afternoon at 3pm. Read this. A 30-day visa costs 690 dh and is now valid from a date you specify on your application, not the date of issue. For photos and copies there is a supermarket at the crossroads about 100 metres away (N33° 58.93′ W06° 49.75′; opens at 7.30am).

The Mali embassy is in the same street, 100m away.
7, Rue Thami Lamdawar
Rabat-Souissi
GPS N33 58.8′ W06 50.0′

There is also a Mali embassy in Nouakchott with visas issued in as little as an hour on a good day. From Mali northwards into Mauritania: ‘At Nioro they are no longer issuing visas at the border... you can get a visa at Bamako near the Chinese Embassy on Rue Kolikoro. You need 4 photos; ready next day for 20,000 CFA.’

Border formalities from Morocco
Both open from around 8.30 to 18.00, give or take. Best to arrive early in the day.
Allow up to half a day from arriving at the Moroccan frontier at Guergarat (left) to leaving the Mauritanian post towards the Nouadhibou–Nouakchott road.

Having come a few kms across from the Moroccan frontier (N21° 21.8′ W16° 57.6′) on the partly sealed Moroccan road through ‘No Man’s Land’ (or technically, PFZ territory – green on map above left), you reach the buildings at the start of the Mauritanian tarmac (N21° 20.0′ W16° 56.8′) where you get stamped by the Gendarmerie. Buy a visa if necessary or have your pre-obtained visa stamped by the Police. No passport photos or photocopies needed: they photograph you with a webcam, fingerprint you and scan your passport.

By now a fixer will have nabbed you and offer to do it all for you for a fee from €10. Like in Wadi Halfa (Sudan) it’s a bit of a scam, in that you could DIY but there’s no getting away from paying the fixer. You will get all your docs sorted so just accept it good-naturedly as a ‘tax’. Your fixer may do all the procedures listed below.

Next, get a white A4 30-day temporary import permit (TIP: 480 oogs) and optionally buy official currency if you didn’t buy black in No Man’s Land.
Then buy vehicle insurance, a windscreen sticker which costs 950 oogs for a car for 10 days, less for bike. Or you can buy a forward-dated ‘Carte Brun’ for the ECOWAS West African countries (not Mauritania) for €75 (320 oogs) for a car. This is regional motor insurance, similar to the regional laisser passer ‘local carnet’.
Note that they now search your vehicle a little more thoroughly and may not take to lashings of cheaper Moroccan fuel in jerricans or alcohol.

In 2007 a guy was needlessly killed and another badly injured but a landmine while straying east just a couple of kms from the unsealed track through No Man’s Land. Full story and maps for clarification here. Locals (possible evading the border) were also killed in this way in 2009. If you stick to the 3km track there is zero risk, even if travellers’ blogs routinely exaggerate the deadly experience of ‘crossing a live minefield’ to reach Mauritania.

Nouadhibou to Nouakchott
Following the kidnappings in 2009, the Mauritanians got on the case and there are now several checkpoints on the road from Nouadhibou to Nouakchott and at key junctions all over the country. As in Western Sahara, handing out a pre-printed form (left) with your details saves time. You can download a Word template by clicking this. Adapt as you wish but make at least two dozen.
The Route d’Espoir from Nouakchott east to Nema is also patrolled but thought to be less safe. If you are a conspicuous foreigner venturing east beyond Ayoun may be unadvisable. Avoid crossings into Mali east of Ayoun; what’s left of AQIM or general-purpose bandits still operate there. October 2018 report of travelling to Oualata.

The ore train
Apparently the ore train linking Nouadhibou port with the iron mines at Zouerat no longer allows you to offload vehicles at Choum on the ‘corner’ of the PFZ. Motorbikes might be manhandled on and off, but it still carries cars all the way to Zouerat (12–16hrs) even though asphalt now runs to Zouerat and beyond. Good northern Mauritania and PFZ report from 2017. There is no formal reservation system, booking website or even a station. There will be a yard at each end with a car ramp.

The Tindouf Route – border with Algeria
After nearly 70 years, by the winter of 2019 a couple of southbound tourists had used this reopened border since its announcement in 2018. Because of Algerian visa issues, it’s easier in this direction, but you may find difficulties in getting permission to do it via an agency, most of who don’t know anything about it.

The old map left indicates colonial-era tracks; today’s tracks may follow a slightly different route. For track-and-tree level aerial imagery, Bing in much better than Google in this part of the Sahara. And Esri (Apple Maps) can be even better but has a poor user interface.
More on Trans Sahara Routes.

The southern border with Senegal 
The ferry at Rosso (map left) has a bad reputation as a place of low-level scammery, with officials working with uninformed locals. It has been like this for decades so southbound, many choose to avoid the ferry at Rosso and head 30km downstream to the dam or ‘barrage’ at Diama where things are usually less bad. There is no ferry here – you cross the tidal lifting bridge.
You leave the N2 highway way north of Rosso. The road to the southwest is now sealed, maybe all the way to Diama, certainly for the first 20km.

Desert pistes
Note the differing views (left) from the British and French foreign ministries on where is safe to travel in Mauritania. In my opinion and recent experience, the French version is far more realistic, as is the other zoned map below which, unlike the two above, does not cut off access from Moroccan-occupied Western Sahara near Nouadhibou.

A lot of overlanders still shoot through Mauritania and don’t give the interior a chance. Others in less of a rush recognise that these days it’s the only real Saharan country left where you can drive anywhere they’ll allow without a mandatory guide, although lately, they might insist you get to a town before dark and camp by a police station.

The run inland to Choum along the railway (Route R2, below) is a good introduction to the desert with easy navigation with some extended low dune cordons. It gets soft and tussocky so for these sections motorbikes may find it easier on the coarse gravel between the rail tracks (no sleepers). Once you reach Choum there is asphalt south to Atar and north to Zouerat, with plans to extend it all the way to Algeria. Few tourists go to Zouerat; a huge iron mine, and still fewer venture up to Bir Mogrein which is the end of the road.

In spring 2018 it was reported the old 400-km Route R10 (from Sahara Overland) between Atar and Tidjikja was obsolete, with a new road finished in 2023 (below). Tidjika has long been on the road network. This new red road opens up access into the interesting Adrar region which is more dramatic in the north and east (near Atar). Elsewhere the canyons (or fault lines) of the Adrar plateau can get dune chocked or are slow and stony on the plateau stages, though Berbera guelta (left) is worth a visit, along with the well-known tourist guelta of Terjit, just out of Atar. Otherwise, a good run in a 4×4 would be up the sandy Tifoujar pass and out over the Amatlich erg back to the N1 highway near Akjoujt. Or out east to Ouadane, Guelb and Gallouiya then back west along the plain below the Adrar escarpment.

Actual tracks are rare on the 800-km R11 piste following the Dhar Tichit escarpment between Tidjikja via Tichit to Nema and, being close to Mali, Nema may not be a good place to end up these days. Full details of these tracks and more in the old book or good trip report here from 2013.

North of Choum is little explored, but possibly not actually out-of-bounds on the northwest corner west of 10°W (see this). You won’t make it to Chegga fort where Mali and Algeria meet; there’s probably too much illicit activity going on around here. The map on the left shows access in 2017; basically Bir Mogrein is the limit.

Bab Sahara is a popular place to stay in Atar. On the west side of town. That map above is produced by them and you’ll find vendors selling it in Atar and Chinguetti.

The old Route R2 update from the border via Choum to Atar (520km, p.468 in the old book) is left. Since 2011 it’s said to be improved although the dunes stages are still dunes and would be hard work on a heavy bike and even harder in a 2WD.
A Google map with added information.

In late 2006 we drove direct from Ouadane east across northern Mali and Algeria right up to the Libyan border beyond Djanet, a technically easy if very remote 2000km off-piste traverse that was not without risks in northern Mali and would be unthinkable today. Another trip report from far north Mori in late 2011 here. Stick to the Zouerat road and you should be OK, but of course it’s a dead-end, as borders beyond are closed – to tourists at least.