Where should I store shared values?

I have several variables that I will need to access from many places, including multiple Activity(s), Adapter(s), and many others. I am sure this is not an uncommon scenario. In UWP, I was able to use App.xaml.cs, but as far as I know there is no equivelant to this in Android Native. Where is the best place to store variables that I need to access from all places? Thanks.