When connecting to PostgreSQL I get a Database Does Not Exist error

psql: FATAL:  database "defaultdb" does not exist

A Database Does Not Exist error occurs when:

• You connect to the wrong cluster.
• You connect to a database that doesn’t exist in your specified cluster.

If you are getting this error:

• Verify that you are using the correct hostname to connect.
• Verify that you’ve created the database in your cluster of choice.