Louis dressing is a traditional salad dressing originating from the United States of America. It's based on mayonnaise and additions such as green onions, minced green chili peppers, red chili sauce, celery salt, parsley, lemon juice, and sometimes ketchup.

It's usually used as a dressing for seafood salads such as crab Louie or shrimp Louie. Before topping the dish, the dressing should be well chilled. The origins of Louis dressing are disputed, with restaurants in Seattle, Spokane, San Francisco, and Portland claiming to be the home of the original dressing, which dates back to the 1900s or 1910s.