A fixed-rate mortgage (FRM) is a mortgage loan where the interest rate on the note remains the same through the term of the loan, as opposed to loans where the interest rate may adjust or "float". As a result, payment amounts and the duration of the loan are fixed and the person who is responsible for paying back the loan benefits from a consistent, single payment and the ability to plan a budget based on this fixed cost.

Other forms of mortgage loans include interest only mortgage, graduated payment mortgage, variable rate mortgage (including adjustable-rate mortgages and tracker mortgages), negative amortization mortgage, and balloon payment mortgage. Unlike many other loan types, FRM interest payments and loan duration is fixed from beginning to end.

Fixed-rate mortgages are characterized by amount of loan, interest rate, compounding frequency, and duration. With these values, the monthly repayments can be calculated.

Fixed-rate mortgages are vulnerable to inflation risk, which means that borrowers with such mortgages are better off under unexpectedly high inflation (as the inflation lowers the real present value of their loan repayments), while they are worse off if there is a drop in inflation that lowers interest rates. Fixed-rate mortgages usually charge higher interest rates than those with adjustable rates. According to scholars, "borrowers should generally prefer adjustable-rate over fixed-rate mortgages, unless interest rates are low."