The high speed line from Paris to Lyon is the oldest in Europe, dating back to 1981. During the following years the line has been continuously extended towards the Mediterranean until it reached Marseille in 2001. Frequent TGV trains connect Paris with the second and third largest cities of France, bringing you in just about two hours to Lyon and in roughly three hours to Marseille. Get aboard the fastest trains in Europe, running at up to 320 km/h between Avignon and Aix-en-Provence, overtake cars on the parallel motorways with ease and enjoy the landscape fly by. However, if you prefer to travel the traditional way, you can also go with regional trains along the original route of the PLM (Paris Lyon Mediterranne) which once saw such famous trains as "Le Mistral" or "Le Train Bleu" which were eventually replaced by TGV.
UPDATE: Since 2017, SNCF is rebranding its famous TGV high speed trains as "inOui". We still love the old name so we'll use both names in the future.
Train tickets for Paris - Lyon - Marseille
Tickets for all trains are available online at Trainline or Oui.sncf. Trainline is a great booking tool for trains in France. It requires a free registration but is very easy to handle and gives you the best available prices. Of course tickets are also available locally at ticket desks or ticket machines at stations. If you have to board a train without a ticket, immediately look for the conductor to avoid being fined. In principle, there are three different fares available:
Prem: No return or exchange; these are usually the cheapest but have limited availability and have to be purchased well in advance
Loisir: Free return or exchange until one day prior to departure; more expensive than Prem but usually available until one day prior to depature; the earlier you book the more you save compared to Pro
Pro: Free return or exchange; available until departure, full fare
Several reductions are available for travellers under 26 and from 60 years of age as well as for concession card holders.
TGV require compulsory reservation which is included in regular tickets. If you are travelling with a Rail Pass such as Interrail or Eurail you can book this reservation easily online at rail.shop/sncf/reservation. Currently the standard reservation price is 10€, however the number of seats available for this price is limited on each train - if sold out, you have to pay 20€. This more expensive reservation is available anytime (as long as the train is not fully booked) and not limited.
There are no inOui (TGV) services from Paris calling at both Lyon and Marseille, services to stations south of Lyon bypass the town in the east. inOui/TGV from Paris to Lyon are usually non-stop and run hourly throughout the day with additional services at peak times. In Lyon, all trains call at Part-Dieu station and most of them continue to Perrache station. TGV/inOui from Paris to Marseille run hourly with a few exceptions and usually also call at Avignon and Aix-en-Provence. Note that these are the "TGV stations" which are not directly in the city centre. From Avignon TGV frequent connecting trains run to Avignon Centre while regular buses connect Aix-en-Provence TGV with the city centre. In Paris, TGV/InOui start from Gare de Lyon and arrive at St Charles station in Marseille.
Usually all services from Paris to Lyon and Marseille are operated by TGV Duplex double-deck trains. All trains convey 2nd and 1st class accomodation as well as a bar coach in the middle of the train, offering small snacks and drinks. Personally, I would recommend to book a seat on the upper deck of the train since the view from there is much better of course. However, since the corridor through the train is located on the upper floor it is usually much busier with passengers walking through the train on the way to the toilets or to the bar - so if you are looking for more silence and privacy to work or to read a book it might be a better idea to book a seat on the lower deck. When booking tickets you can easily request a seat on the upper or lower deck.
From December 2018 onwards "inOui" trains are used on Paris - Marseille services. These services will have WiFi onboard.
In addition to the fast TGV services there is still the option to travel from Paris to Lyon and Marseille using conventional "TER" regional trains. These trains run via the classic PLM route via Dijon - Beaune - Lyon - Orange - Avignon - Arles and take about five hours from Paris to Lyon and about nine from Paris to Marseille. These regional trains run about every two hours from Paris to Lyon and every two hours from Lyon to Marseille. At Lyon Part-Dieu you have about half an hour to change trains.
The TER regional trains on this route are trains formed of a locomotive plus classic "Corail" rolling stock. They convey both 2nd and 1st class seating and are quite comfortable, especially in first class. However trains do not have a restaurant or bistro service so you have to bring something to eat and drink by yourself.
If you want to travel from Paris to Lyon or Marseille using regional trains and want to buy tickets online, you would have to get separate tickets for Paris - Lyon and Lyon - Marseille.
You can find some example schedules for both TGV/inOui and TER connections here:
Paris - Lyon | Paris - Marseille
Update: November 2018