Here are my go-to travel apps these days. I typically put these in a folder on the first page of my phone so that I can access them easily. Make sure they are downloaded/updated, and you are logged in if you will be out of cell service.
1) WhatsApp / Skype
WhatsApp is used internationally for free texting and calling (both users must have number on WhatsApp). Skype is another option for making international calls — cheap but not free, but you can all any number even if they are not on Skype.
2) Wallet
Keep your airline boarding passes in your Wallet. Also your Priority Pass card if you have one.
3) Airline Apps
Include the airlines you are flying on so that you can check-in and get notified of any changes.
4) Google Translate
A great way to translate menus and even talk with people. Download the language in your area.
5) Google Maps / Rome2Rio
Download the area where you are going in Google Maps so that you can view the map offline. It may have the local bus and train schedules. Rome2Rio can also help figure out how to get between cities.
6) MapMyRun / Strava
If you are hiking, these are great apps to track your hike.
7) Uber/Lyft/Lime/Bolt
Ride share, bikes, and scooters depending on the area.
8) GPSmyCity
This is a tour app for popular tourist cites and towns. It is a great option if you like to explore on your own.
9) PeakFinder/Night Sky
Fun apps in the mountains and in a dark sky.
10) Photos
Create a folder of travel photos you will need — passport, drivers license, travel insurance, travel itinerary, etc.