"Whew!" is an expression we use to show relief, exhaustion or surprise, but it's sometimes overused, and it may sound less emphatic or even childish sometimes. So, if you want to convey the same message of relief or surprise, but with slightly different variations, you can use some synonyms. Some common alternatives for "Whew!" are "Phew!", "Thank goodness!", "Thank heavens!", "Wow!", "Geez!", "Lordy!", "Easy now!", "That was close!", "My goodness!", and "I can breathe again." By using these synonyms for "Whew!" you can make your writing or conversation more interesting and avoid using the same phrase repetitively.