A designated marksman (DM), squad advanced marksman (AD) or squad designated marksman (SDM) is a military marksman role in an infantry squad. The term sniper was used in Soviet doctrine although the soldiers using the Dragunov SVD were the first to use a specifically designed designated marksman rifle. The analogous role in the Israel Defense Forces is sharpshooter.

The DM's role is to supplement the attached squad by providing accurate fire upon enemy targets at distances up to 600 metres (660 yd). Due to the need for repeated effective fire, the DM is usually equipped with a scoped semi-automatic rifle called a designated marksman rifle (DMR). Like snipers, DMs are trained in scouting and precise shooting, but unlike the more specialized "true" sniper (who often operate independently), they operate as an intrinsic part of an infantry fireteam and are tasked to lay down accurate support fire at valuable targets as per tactical necessity, thus extending the reach of the fireteam.

The growth of the DM rifle can be attributed to two main influences; the near-universal adoption of intermediate cartridges, such as 5.56×45mm, 5.45×39mm, and 7.62×39mm for standard service rifles, which limit the typical effective range of a standard infantryman to within 200–300 metres (220–330 yd); and the increasing specialization over the last 15 years (mid-2000s to late 2010s) of Western sniper rifles and their employment of more powerful rounds, such as .300 Winchester Magnum and .338 Lapua Magnum, which are more suitable for targets beyond 600 metres (660 yd). These two influences have left a gap in the firepower of the rifle platoon that a more accurate optic-equipped service rifle derivative can usefully fulfill, especially in theaters such as Afghanistan where the shortcomings of standard 5.56mm service rifles at ranges over 300 meters became apparent.