Yes, you almost certainly will need a GS1 GTIN for each product you wish to sell on Amazon.
Amazon requires GS1 GTINs in many of their product categories so you will need a licence from GS1 to list on Amazon.
GS1 GTINs help Amazon distinguish products from each other and to manage their platform more efficiently. Other marketplaces and retailers around the world also rely on GS1 GTINs and using them will make it easier to expand your business online and offline globally.