The following were the results of the finals only of each of the Men's 100 metre backstroke events in each of the classifications. Further details of each event, including where appropriate heats and semi finals results, are available on that event's dedicated page.
The S1 category is for swimmers who may have tetraplegia, or some form of loss of muscular power in their legs, arms and hands. These swimmers would regularly use a wheelchair.
The final in this classification took place on 25 August 2021:
The S7 category is for swimmers who have one leg and one arm amputation on opposite side, or paralysis on one side of their body. These swimmers have full control of their arms and trunk but variable function in their legs.
The final in this classification took place on 30 August 2021:
The S11 category is for swimmers who have severe visual impairments and have very low or no light perception, such as blindness, they are required to wear blackened goggles to compete. They use tappers when competing in swimming events.
The final in this classification took place on 28 August 2021:
The S12 category is for swimmers who have moderate visual impairment and have a visual field of less than 5 degrees radius. They are required to wear blackened goggles to compete. They may wish to use a tapper.
The final in this classification took place on 27 August 2021:
The S13 category is for swimmers who have minor visual impairment and have high visual acuity. They are required to wear blackened goggles to compete. They may wish to use a tapper.
The final in this classification took place on 26 August 2021:
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