三弦中国弹拨乐器。张3根弦，故名“三弦”。或为秦朝乐器“弦鼗”所演变而成。其名最早出现于明杨慎《升庵外集》：「今次三弦，始于元时」。而清毛其龄《西河词话》：“三弦起于秦时，本三十鼓鼓之制而改形易响，谓之鼓鼓，唐时乐人多习之，世以为胡乐，非也”。

在昆曲、淮海戏、大弦子戏等戏曲与单弦、大鼓、三弦书等曲艺中为主奏乐器，亦用于京剧的「三大件」、江南丝竹的「八大件」、广东音乐的「五架头」。由于其独特音色，在民族乐团中有重要的地位。有大量由戏曲伴奏音乐和古琴曲移植的合奏曲，却缺乏专为发挥三弦特色之独奏曲。

流行于中国北方的三弦称为大三弦、大鼓三弦、京三弦，一般长122厘米，流行于中国南方的三弦称为小三弦、曲弦、南三弦、南弦子，一般长95厘米。

The sanxian (Chinese:三弦, literally "three strings") is a Chinese lute — a three-stringed fretless plucked musical instrument. It has a long fingerboard, and the body is traditionally made from snake skin stretched over a rounded rectangular resonator. It is made in several sizes for different purposes and in the late 20th century a four-stringed version was also developed. The northern sanxian is generally larger, at about 122 cm in length, while southern versions of the instrument are usually about 95 cm in length.