The calculated distance (air line) between Lille and Fontenay-sous-Bois is approximately 126 miles respectively 202 kilometers.
By car or train, the actual journey to Fontenay-sous-Bois is certainly longer, as only the direct route (as the crow flies) between Lille and Fontenay-sous-Bois has been calculated here.
Air line (approximately)
202 kilometers
109 nautical miles