Mordechai Yitzchak HaLevi Willig (born April 25, 1947; 5th of Iyyar, 5707 on the Hebrew calendar) is an Orthodox rabbi and rosh yeshiva at Yeshiva University in Washington Heights, Manhattan. He is often known to his students as the Ramu (רמ"ו), which is the transliteration of the acronym of the Hebrew letters Reish, Mem, and Vav, which spell out the first letters of Rav Willig's name (Rabbi Mordechai Willig = רב מרדכי וויליג).