Luggage lockers and baggage transfer what you can do with your bags.

Nannybag: This is a company that has partnered with shops and hotels to bring you a secure luggage storage service (more than 2,000 secure lockers located in over 250 cities in Europe and America). Just choose a location and book a slot via the website or through the app (reservations can be made 24/7).
Price: €6 per bag for 24 hours. 

Stasher: Set up in 2015, this UK-based company was one of the first platforms to offer a luggage storage service in shops and hotels. It has entered into partnerships with major groups such as Accor to allow users to benefit from an extensive network that comprises more than 1,000 locations in over 100 cities worldwide.
Price: €6 per bag per day, and €5 for each additional day.

Holibag: Along the same lines, the Holibag site and app let you leave your luggage with partner retailers: some 500 in eleven countries throughout Europe (France including Guadeloupe, Germany, Belgium, Denmark, Spain, Italy, Netherlands, Portugal, United Kingdom, Sweden, and Switzerland).
Rate: €3.90 for 4 hours, €5.90 for 6 hours, €7.90 for 12 hours, and €11.90 for 24 hours. 

Bagbnb: With cafes, bike rental shops, bars, and hotels, the service is based on a thousand partner points called 'Angels' in worldwide locations that make up the network of this platform specialising in luggage storage. Being part of the network also gives Angels the chance to promote their services to travellers and pass on tips on good places to go.
Price: €5 per bag per day in Europe. 

City Locker: With City Locker there no partner establishments but rather secure automated lockers, and this is how it works: you log on to the website using your smartphone, tablet or computer, choose an address, date, and the length of time you require (an hour or a day), then book. A code is sent to you by email or text message, allowing you to open the locker and deposit your luggage. For the moment, however, City Locker only exists in a few countries; France, Greece, and Algeria (city centre, near train stations and airports access areas) and luggage can only be left from 8am to 10pm.
Price: from €7 per day per locker depending on the location.

Stow Your Bags: If your business trip takes you to Italy (Rome, Milan, Florence, Naples, Venice, Catania, and Pisa) or Spain (Madrid, and Barcelona), you will not be able to miss Stow Your Bags' bright yellow and brown lockers. Book online by selecting the size of the locker you require (a standard locker holds two cabin-sized bags, and the XXL version holds four cabin-sized bags), the length of time you require and the location. You will find a map that shows you the distance between your locker and the city's key locations (stations and tourist sites).
Price: varies according to the city. For example, in Milan the rate is €1.49 per hour for a standard locker or €12.99 per day.

Eelway: Created in 2016, this startup offers a real tailor-made baggage management service. Services range from luggage storage to managing your bags when you arrive at the airport or station, with concierges in yellow vests who transfer them to your hotel or home. The company also offers a worldwide baggage delivery service. Everything is done online (bookings, quotes, and payment). Bags are sealed and insured. You can also track your baggage step by step on your smartphone.
Price: €10 per bag per day for storage, from €25 for baggage transfer in Paris and inner suburbs, from €10 for international delivery.

Tripperty: Introduced in 2018 by the Paris Airport Group (ADP), La Poste, and Bagages du Monde, Tripperty is a storage and transfer service for items confiscated at security. Given a bottle of Grand Cru to celebrate a deal but left it in your carry-on bag? No problem, all you need to do is use the Tripperty app and choose to either leave your personal item in a Trippertybox at the airport the time you return to pick it up or have it posted to an address of your choice. Trippertyboxes are currently only available at Terminal 3 and Halls 2E and 2F at Charles de Gaulle airport in Roissy, along with Marseille Provence, Ajaccio, and Nice airports.
Price: €10 for storage at the airport, €16 to have an item posted in France, €22 in Europe and €32 for international postage.