向日葵（学名：Helianthus annuus）是菊科向日葵属的植物。别名太阳花或向阳花，但易与非洲菊混称，一般应称向日葵。因花序随太阳转动而得名。

一年生草本，高1～3.5米。茎直立，圆形多棱角，质硬被白色粗硬毛。广卵形的叶片通常互生，先端锐突或渐尖，有基出3脉，边缘具粗锯齿，两面粗糙，被毛，有长柄。头状花序，直径10～30厘米，单生于茎顶或枝端。总苞片多层，叶质，覆瓦状排列，被长硬毛，夏季开花，花序边缘生中性的黄色舌状花，不结实。花序中部为两性管状花，棕色或紫色，能结实。矩卵形瘦果，果皮木质化，灰色或黑色，称葵花籽。

Helianthus annuus, the common sunflower, is a large annual forb of the genus Helianthus grown as a crop for its edible oil and edible fruits (sunflower seeds). This sunflower species is also used as bird food, as livestock forage (as a meal or a silage plant), and in some industrial applications. The plant was first domesticated in the Americas. Wild Helianthus annuus is a widely branched annual plant with many flower heads. The domestic sunflower, however, often possesses only a single large inflorescence (flower head) atop an unbranched stem. The name sunflower may derive from the flower's head's shape, which resembles the sun, or from the false impression that the blooming plant appears to slowly turn its flower towards the sun as the latter moves across the sky on a daily basis.