A mattress protector includes a composite sheet having a non-deformed length and a non-deformed width. The composite sheet includes a fabric and a water impermeable polymer. The composite sheet is capable of repeatedly stretching to a deformed length of at least 115% of the non-deformed length and returning to within 8% of the non-deformed length without rupture or permanent wrinkling of the composite sheet. Mattresses may be covered and protected by such a mattress protector. Methods of forming mattress protectors include providing a water impermeable polymer on a fabric so as to form a composite sheet having a non-deformed length and a non-deformed width, and formulating and configuring the composite sheet so as to be capable of repeatedly stretching to a deformed length of at least 115% of the non-deformed length and returning to within 8% of the non-deformed length without rupture or permanent wrinkling of the composite sheet.