You can book a room on Booking or on AirBnb  

Here are some hotel and youth hostel recommandations in downtown Lille:

HI Lille - youth hostel

235 boulevard Painlevé, 59000 Lille

(400m from the Porte de Valenciennes subway station, 10min from Gare Lille Flandres)

From 20€ (a single bed in a six-bed dormitory)

For further information and to book a bed

The People - youth hostel

109 rue de Saint André, 59000 Lille

(1,5km by foot from Gare Lille Flandres, 80m from the Magasin bus stop (bus line 10, possibility to take it from Gare Lille Flandres))

From 27€ (a single bed in a six-bed dormitory)

For further information and to book a bed 

Hotel Brueghel***

5 Parvis Saint-Maurice, 59800 Lille

(300m from Gare Lille Flandres, 800m from Gare Lille Europe, and 300m from the Rihour subway station)

From 109€ (for a single) to 159€ (for a double) per night 

For further information on the hotel and to book a room 

Ibis budget Hotel Gares Vieux Lille**

10 rue de Courtrai, 59000 Lille

(800m from Gare Lille Flandres, and 950m from Gare Lille Europe)

From 89€ (for a single, double, or triple)

For further information and to book a room