果酸（AHA、α-Hydroxy acids、alpha hydroxy acids），是指由多种天然蔬果中所萃取的自然酸，由于绝多数均自水果中提炼，因而俗称为果酸，但也有人合成的。这类有机酸中，羟基取代了和羧基相邻的碳原子。例如甘醇酸、苹果酸、酒石酸、柠檬酸、乳酸等。果酸的种类多，但以甘醇酸以及乳酸最为广用。果酸被广泛用于化妆品中，这些化妆品宣称能够减少皱纹，减缓衰老，改善皮肤。果酸也是医院里治疗皮肤疾病的常用药，也用于spa中，浓度通常为4%。果酸的一些疗效已经被确认，但部分化妆品仍有夸大疗效的嫌疑。

α-Hydroxy acids, or alpha hydroxy acids (AHAs), are a class of chemical compounds that consist of a carboxylic acid substituted with a hydroxyl group on the adjacent carbon. They may be either naturally occurring or synthetic. AHAs are well known for their use in the cosmetics industry. They are often found in products that aid in the reduction of wrinkles as well as to soften strong, defining lines and improve the overall look and feel of the skin. They are also used as chemical peels available in a dermatologist's office, beauty and health spas and home kits, which usually contain a lower concentration of around 4%. Effective results through continuous treatment have resulted in AHAs being a successful & developmental method of curbing harsh ageing effects in the skin & cosmeceutical industry.