Quinquagesima is the name for the Sunday before Ash Wednesday. It was also called Quinquagesima Sunday, Shrove Sunday or Esto Mihi. The name originates from Latin quinquagesimus (fiftieth), referring to the fifty days before Easter Sunday using inclusive counting which counts both Sundays (normal counting would count only one of these). Since the forty days of the Lenten fast included only weekdays, the first day of Lent, Ash Wednesday, succeeds Quinquagesima Sunday by only three days.

The earliest Quinquagesima Sunday can occur is February 1 and the latest is March 7.

The reforms of the Second Vatican Council included the elimination of this term for this Sunday (and the two immediately before it - Sexagesima and Septuagesima Sundays), and these Sundays are part of Ordinary Time. The contemporary service books of many Anglican provinces do not use the term but it remains in the Book of Common Prayer. According to the reformed Roman Rite Roman Catholic calendar, this Sunday is now known by its number within Ordinary Time - fourth through ninth, depending upon the date of Easter - or the fourth through the ninth Sunday after Epiphany in the contemporary Anglican calendars, and that of various Protestant polities. The extraordinary form of the Roman rite continues to refer to the Sunday prior to Ash Wednesday as Quinquagesima Sunday, and the two Sundays immediately preceding it as Sexagesima and Septuagesima Sundays.

In 2008, Quinquagesima fell on February 3.