"I have my ticket to Australia."
Translation:J'ai mon billet pour l'Australie.
Country names are almost always used with a definite article: they are feminine if they end in -e (La France...), and masculine otherwise (Le Canada...), with very few exceptions.
City names however are treated as proper nouns and are not used with an article: J'ai mon billet pour Paris.
Some countries are also treated as proper nouns (Monaco, Singapour...), usually they are either island nations or countries small enough to be considered cities.