Bring a large pot of lightly salted water to a boil. Cook elbow macaroni in the boiling water, stirring occasionally until cooked through but firm to the bite, 8 minutes; drain.
Transfer hot macaroni to a large bowl.
Pour Italian-style salad dressing and crushed pineapple over the macaroni; stir.
Add ham, celery, tomatoes, eggs, and onion; stir.
Cover bowl with plastic wrap and refrigerate until chilled, at least 1 hour.