星期六，又称礼拜六或周六。指的是一周中星期五之后、星期日之前的那一天。星期六的拉丁语名字是dies Saturni，意思是萨图尔努斯日或土星日；法语是Samedi，来源于拉丁语词，意思是“安息日”；英语是Saturday，可能来源于土星；俄语是суббта，意思是“安息日”。

在古代中国、台湾日治时期和现在的日本、韩国、朝鲜，一星期以「七曜」来分别命名，星期六叫土曜（yào）日（韩语：토요일）。在中国民间口语称礼拜六，在台湾话也简称拜六。由于是每个星期的最后一日，通常叫周末。

根据《圣经》的描述，星期六是上帝以六天时间创造万物后的第七天，上帝在这一天休息。按照《圣经》的《十诫》，是为安息日，犹太教和一些基督教派以这一天作为崇拜的日子。

Saturday is the day of the week following Friday and preceding Sunday. Saturday is the seventh and therefore last day of the week according to many commonly used calendars, and it is the second-to-last (sixth) day of the week according to ISO 8601 (see below). The Romans named Saturday Sāturni diēs ("Saturn's Day") no later than the 2nd century for the planet Saturn, which controlled the first hour of that day, according to Vettius Valens. The day's name was introduced into West Germanic languages and is recorded in the Low German languages such as Middle Low German sater(s)dach, Middle Dutch saterdag (Modern Dutch zaterdag) and Old English Sætern(es)dæġ and Sæterdæġ. However, the name was selected as a calque of the god Saturn, after whom the planet was named. The day was also referred to as "Sæternes dæġe" in an Old English translation of Bede's Ecclesiastical History of the English People. In Old English, Saturday was also known as sunnanæfen ("sun" + "eve" cf. dialectal German Sonnabend).