A loan servicer is a private lending company contracted by the Department of Education (ED) to handle billing and other services for federal student loans on behalf of the federal government. Federal student loans are owned by ED, but loan servicers are responsible for facilitating loan repayment. They are required to offer students repayment options such as income-driven repayment plans and loan consolidation.

Loan servicers are assigned after a loan has been disbursed and should contact students directly.

Students can identify their loan servicers several ways:

On their Studentaid.gov account dashboard under the "My Loan Servicers" section: https://studentaid.gov/dashboard/.
On the National Student Loan Data System (NSLDS) website under "Financial Aid Review": NSLDS: National Student Loan Data System.
By calling the Federal Student Aid Information Center (FSAIC): 1-800-433-3243 (1-800-4 FED AID).

Students and graduates should never pay "enrollment," "subscription," or "maintenance" fees for services relating to their federal loans such as loan consolidation or income-driven repayment plan applications. These services must be offered by loan servicers free of charge.

Student borrowers should contact their loan servicers when they

Withdraw from school,
Graduate,
Drop below half-time enrollment, or
Stop going to school.

After graduation, students should contact their loan servicers when they

Change their name, address, or phone number;
Need help making a loan repayment;
Have a question about their bill; or
Have other questions about their loans.

Current loan servicers include Edfinancial, MOHELA, Aidvantage, Nelnet, ECSI, Default Resolution Group, and CRI. However, this list is subject to change, and borrowers should expect their loans to change hands over the life of their loans. If the government changes your loans from one servicer to another, you should receive an email or letter from the new servicer with any actions that you need to take. No changes to your loans should occur. Loans then need to be paid to the new servicer, so if you have enabled a bank or bill paying service, the provider should be given your new servicer's contact information. You may also need to create a new online account with the new servicer.

Additional Resources:

Who’s My Student Loan Servicer? | Federal Student Aid

Federal Student Loan Servicers: Who They Are and What They Do - NerdWallet