Preheat an outdoor grill for high heat and lightly oil the grate.

Mix ground beef, onion, crushed crackers, egg, and ranch dressing mix together in a bowl until well combined. Form into eight hamburger patties.

Cook patties on the preheated grill until no longer pink in the center, about 5 minutes per side. An instant-read thermometer inserted into the center should read at least 160 degrees F (70 degrees C).