The Nantes to Brest canal is the great Breton dream, and it comes with a catch that nobody mentions in the brochures: you cannot actually do it end to end by boat anymore. I learned this the slightly embarrassing way, having half-planned a one-way passage across Brittany before a Frenchman at a Redon pontoon gently explained why my plan was impossible. Once you understand the catch, though, the canal becomes one of the loveliest cruising grounds in France. Here is how it really works.
The canal that was cut in two
As built in the nineteenth century, the Nantes to Brest canal ran roughly 385 kilometres with around 238 locks, stitching together a string of Breton rivers, the Erdre, Vilaine, Oust, Blavet, Hyères and Aulne among them, into a single inland route. It was a strategic project, partly to supply Brest by a route the British navy could not blockade.
Then in the 1920s and 30s they dammed the Blavet at Guerlédan to make a reservoir and a hydroelectric scheme. The dam drowned a stretch of the canal and its locks. That dam is why the through-route no longer exists. The water above and below it no longer connects for navigation, so the canal today is a set of separate cruising sections rather than one continuous waterway.
The sections that are open
Think of it as several distinct cruises, each worth doing in its own right.
The eastern end, Nantes to Redon, runs about 95 kilometres and connects with the Vilaine and the wider waterway network, including the Canal d'Ille-et-Rance up towards Saint-Malo. This is the gateway and the easiest water.
From Redon, the long central section pushes north and west through the Oust valley towards Pontivy. The Redon to Pontivy run is the heart of it, something like 91 locks over roughly 118 kilometres, and it is the part most private and hire boats spend their time on. This is where the famous towns are.
At Pontivy the Blavet branches off and runs down to Hennebont near the coast, about 60 kilometres of river navigation, a worthwhile cruise in itself.
West of the Guerlédan dam, a restored 15-kilometre stretch with 10 locks survives up to the chapel of La Pitié, a heritage run rather than a through-route. And beyond, the Aulne section gives you river cruising down towards the Rade de Brest. They are good water, just not joined to the rest.
The central run: Josselin and Pontivy
If you only do one part, do Redon to Pontivy. The canal here threads through a chain of small heritage towns, the Petites Cités de Caractère, and the jewel of them is Josselin.
We tied up below Josselin on a wet July evening in 2024 and the rain stopped just as the chateau came into view, three round towers rising straight off the water, floodlit later that night. It is one of the great canal views in France and the mooring is right there beneath it. We stayed two nights and walked the old streets above the basin between rain showers.
Pontivy, at the top of the section, is a planned town with a Napoleonic grid and a stout chateau, a good place to provision and a natural turn-around point. Between the towns the Oust valley is green, quiet and full of the herons and kingfishers that make Breton canal cruising what it is.
What it is like to actually cruise
The locks here are largely hand-worked or keeper-attended rather than fully automated, and the central section gives you plenty of them. Lock hours follow the usual French pattern, roughly nine to seven with the lunch hour closed, so you plan around the keepers' clock the same as anywhere. The pace is the gentle canal 6 km/h, and you will rarely want to push it.
Two practical warnings from experience. First, draught. Parts of the Nantes to Brest are shallow and weed up in high summer, so keep your draught modest and check current notices with VNF before you set off. The standard Freycinet gauge canal dimensions apply in theory, but the reality on some Breton stretches is less generous, especially at the banks. Second, weed. Late summer brings floating weed that loves a propeller, so carry a boat hook and be ready to clear it.
Mooring is mostly easy and often free against the bank or at village haltes, with serviced ports in the bigger towns. We free-moored most nights, which keeps Brittany cheap. If that side of canal life is new to you, the detail is in my piece on canal mooring in France.
Connecting waters and the wider network
The thing that rescues the Nantes to Brest from its broken middle is how well its open sections link to other Breton waterways. From Redon you are on the Vilaine, which runs down to the sea at Arzal and up towards Rennes, and from Rennes the Canal d'Ille-et-Rance carries on north towards Saint-Malo and the Channel. That means a boat the right size can string together a genuine Brittany loop without ever needing to pass Guerlédan.
This is where it pays to think about the whole regional system rather than a single canal. A typical foreign cruiser's Brittany season might combine the central Nantes to Brest run with the Vilaine and the Ille-et-Rance, with a coastal hop in between if the boat is up to it. The licences and the VNF vignette cover the inland sections the same way they do elsewhere, scaled to boat length.
The other reward is the variety. Few French canals mix river and canal navigation the way the Breton system does. One day you are working a tight flight of locks in a wooded cutting, the next you are drifting down a broad, tree-lined river with proper current under you. It keeps the cruising fresh in a way the long, dead-straight canals of the plains do not.
Provisioning and pace in Brittany
Brittany is easy country to cruise for supplies. The canal towns are real working towns, not just tourist stops, so markets, boulangeries and the odd chandler are never far. Josselin, Malestroit, Rohan and Pontivy all gave us good market days, and the smaller villages along the Oust kept us in bread and produce between them.
The pace is the usual gentle canal rhythm: an unhurried morning, locks through the middle of the day with the lunch hour closed, an early stop to find a mooring. Brittany weather adds its own character. We had more rain here than on the Burgundy canals, and the green of the valley is the green it is for a reason. Pack proper waterproofs and treat a wet afternoon as a chance to walk a town rather than push on.
Planning a realistic trip
Because there is no through-route, the sensible approach is to pick one section and cruise it as an out-and-back, or loop via the connecting waterways.
A favourite of mine: enter at Redon, run the central section up to Josselin and Pontivy over a week to ten days, turn around and come back, perhaps detouring down the Blavet towards the coast if you have time. That gives you the best towns, the prettiest valley and a manageable amount of lock work without the frustration of hitting a dam you cannot pass.
The Nantes to Brest is not the canal the maps promise. It is better understood as a handful of separate Breton cruises sharing a name and a history. Treat it that way, choose your section, and Brittany by boat lives up to every bit of its reputation. For the broader rhythm of it, the bread runs and the lock-keeper etiquette, see daily life on the French canals before you go.
