select current_user shows dbo

Question: I'm logged onto a SQL Server 2016 instance  using Windows Authentication and executing SELECT CURRENT_USER. Although I have sysadmin rights - the result always returns dbo.  

What I need is to return my domain account name. Can you help?

Answer: There is a difference between CURRENT_USER and SYSTEM_USER. 

SELECT CURRENT_USER  - Returns the name of the current user. This function is equivalent to SELECT USER_NAME().  

If the current user is a sysadmin privilege , the recordset returns “dbo”, rather than the logon name. Which because your current logon has sysadmin privileges explains the dbo result

SELECT SYSTEM_USER (also synonym for SUSER_SNAME().  -  Returns the login name associated with a security identification number. SELECT SYSTEM_USER will return your domain name