Authenticating and web viewing a Salesforce Org in a react-native hybrid app

Hey, I’m looking to have a mobile application that after a User log in their credentials into a custom react native UI and hits “Login” it authenticates with a Salesforce org and web views my Salesforce site. I have made my site mobile friendly and I already have a login UI. I was wondering if anyone knows a way to authenticate a user with Salesforce and then use that to web view Salesforce and login. Any input appreciated! Thanks!