Quinquagesima, or, in full, Quinquagesima Sunday, is the name for the Sunday next before Ash Wednesday in the Catholic (Universal or Whole) Church Calendar.
The name Quinquagesima 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 Roman Church no longer observes much of the Christian Year, including Quinquagesima and the two immediately before it — Sexagesima and Septuagesima Sundays.
The contemporary service books of many Anglican provinces do not use the term but it remains in the Book of Common Prayer.
The 17-day period beginning on Septuagesima Sunday spanning Sexuagesima and Quinquagesima Sundays was intended to be observed as a preparation for the season of Lent, which is itself a period of spiritual preparation (for Easter). In many countries, however, Septuagesima Sunday marks the start of the carnival season, culminating on Shrove Tuesday, more commonly known as Mardi Gras or Fat Tuesday.