It is Lycosa narbonensis, commonly called a Tarantula. It is in fact a species of Wolf spider not a tarantula. It is also the biggest spider in Europe at about 25mm long- that is body length and does not include legs which in fact are not that long on this species but would add at least another 25/30 mm in length.
It is poisonous, but all spiders are. The majority have very weak poison, just sufficient to kill their prey. Many also have fangs that are too weak to puncture human skin. These chaps could bite you and the poison is sufficiently strong to cause some discomfort.
There is a myth that this spider could kill you and that in order to prevent this happening you have to embark on a long and furious dance called the Tarantella. This has no benefit except to entertain the onlookers.
The wolf spiders are hunters. They do not make a web except to line a tube-like tunnel which they hide in during the day and they emerge at night to hunt and poison their prey. The females produce eggs and when these hatch they look after the young, carrying them round on their backs.
I have found only sparse information on this species, so if anyone knows of a good website with authoratitive information please let me know.
There is a similar species found in Europe called Lycosa tarentella. I believe this has a more southerly distribution. However I do not know the exact distribution of either species. I have only ever seen Lycosa narbonensis once in this region of France.