根汁汽水（Root beer，或称根啤），是一种源于檫木树根（或树皮）制成的甜味碳酸饮料，流行于北美洲。其口味与流行于中国广东地区的沙示汽水类似。

Root beer is a dark sweet beverage traditionally made using the root beer tree Sassafras albidum (sassafras) or the vine Smilax ornata (sarsaparilla) as the primary flavor. Root beer may be alcoholic or non-alcoholic, and may be carbonated or non-carbonated. Most root beer has a thick foamy head when poured. Modern, commercially produced root beer is generally sweet, foamy, carbonated, and non-alcoholic, and is flavoured using artificial sassafras. It may or may not contain caffeine.