Linen Shirts
Linen behaves differently from cotton in ways that affect fit before you even put it on. Untreated linen can shrink several percent on its first wash — garment-washed or pre-shrunk linen (often noted in the product description) is cut closer to its final size, while unfinished linen is sometimes cut with extra room specifically to absorb that first shrink. Two linen shirts in the same nominal size can start from different assumptions about how much room is already built in.
Drape is the other variable: linen doesn't cling or stretch the way a cotton-elastane blend does, so linen shirts are usually cut with more ease (extra room through the body) by design, not by sizing error. A linen shirt in your usual size will often read looser than a dress shirt in the same size — that's typically intentional, not a fit problem.
Because linen creases and relaxes with wear, a shirt that feels structured on the hanger will drape differently after being worn and washed a few times. If a retailer specifies whether a linen piece is pre-washed, that's usually more informative than the size chart alone.
Linen Shirts at retailers
Levi's
Levi's Sunset Camp Cotton Linen Shirt - Men's XXL

COS
Camp-Collar Short-Sleeved Linen Shirt in Light Blue

COS
Embroidered-Detail Linen Shirt

COS
Longline Linen Shirt

COS
Relaxed Linen Shirt in Green

COS
Camp-Collar Short-Sleeved Linen Shirt in Light Blue
Levi's
Levi's Classic One Pocket Standard Fit Cotton Linen Shirt - Men's M

COS
Short-Sleeved Linen Shirt Dress in Red

UNIQLO
UNIQLO Men's Cotton Linen Shirt Short Sleeve, Gray, 3XL

COS
Relaxed Linen Shirt in Light Blue

COS
Oversized Short-Sleeved Linen Shirt in Yellow

COS
Folded-Sleeve Linen Shirt in Beige

COS
Oversized Short-Sleeved Linen Shirt

UNIQLO
UNIQLO Men's Premium Linen Shirt, Yellow, 3XL, 100% Linen

COS
Relaxed Linen Shirt

COS
Embroidered-Detail Linen Shirt in Navy

COS
Longline Linen Shirt

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Textured Knitted Linen Shirt

COS
Camp-Collar Short-Sleeved Linen Shirt in Light Blue

COS
Button-Down Collar Linen Shirt in Navy