When travelling outside Canada and the United States, you may be wondering if you need a voltage converter to charge your device in Europe. Canada, USA, and Mexico outlets deliver 110-120 volts where most of Europe operates on 220-240 voltage. My iPhone wall charger reads "Input: 100-240V" meaning the charger will charge your device as long as your outlet is between 100-240 voltage. This means you do not need to bring an additional voltage converter when travelling to Europe with your iPhone. However, you still need a PLUG ADAPTER to change the prongs from North America (2 parallel flat prongs) to the local outlet configuration.
To summarize, when travelling to Europe, you only need your USB wall charger + prong adapter. I travel to Italy frequently and can confirm you do not need a voltage converter to charge an iPhone (below I have illustrated the configuration I used in Italy).
Standard Apple iPhone Charger North America to Italy Prong Adapter