千屈菜（学名：Lythrum salicaria），为千屈菜科千屈菜属下的一个植物种。被列入「世界百大外来入侵种」之一。

Lythrum salicaria (purple loosestrife) is a flowering plant belonging to the family Lythraceae. It should not be confused with other plants sharing the name loosestrife that are members of the family Primulaceae. Other names include spiked loosestrife, or purple lythrum.