DNA fragmentation refers to the process of separating or breaking DNA strands into pieces. This can occur spontaneously or it can be done intentionally in a laboratory or by cells themselves.

Spontaneous DNA fragmentation is a natural fragmentation process that occurs during apoptosis or programmed cell death. Also known as apoptotic DNA fragmentation, this spontaneous process is a biochemical hallmark of apoptosis.

Intentional DNA fragmentation in the laboratory is often performed before library construction or subcloning for DNA sequences. DNA is fragmented in the laboratory using a variety of methods such as needle sheer, passage through a pressure cell, point-sink shearing, sonication, or nebulization.