As of 2014, there are four major carriers that offer mobile connectivity for tourists, with Orange and SFR having the widest coverage, followed closely by Bouygues Télecom. A copy of your passport is required to purchase a SIM card, with a two day activation period.
Top Prepaid SIM options
1. Orange
Cost: Sims are ($6.50 USD) but include credit, ($6.50 USD) for 150 mb data lasting one week, or ($13 USD) for 500 mb data lasting two weeks. Link
2. SFR
Cost: Sims are ($1.30 USD), ($11 USD) for 1 gb data lasting 7 days. Link
3. Bouygues Telecom
Cost: Sims are ($1.30 USD), ($13 USD) for 300 mb data lasting one week, or ($44 US) for 2 gb data lasting one month. Link
Where to Buy: Recommended to purchase from an authorized outlet
Call for Information: 01 46 21 46 46 (in Paris) OR 39 39
Call for Emergency: 112