Renting a bike in Maastricht is easy if you know where to look! One of the most popular and easy options if you just need a bike for a day is the OV-fiets. The state-owned railway operator NS runs this rental service and you can get your hands on these blue and yellow rentals at most Dutch train stations, including Maastricht. To rent one of these bikes you will need an OV-chipkaart.
If you don’t have an OV-chipkaart or you’re looking to be renting a bike that has gears or suspension (a race bike or a mountain bike, for example) then you should get in touch with a local bike shop and see what they have on offer. Besides the short-term rental options mentioned there are also companies specialised in long-term bike rental. A simple Google search for ‘monthly bike rental’ or ‘maandelijkse fietsverhuur’ will give you some good results.