Rabbi Yehudah HaChassid was one of the main teachers of the Chassidei Ashkenaz and one of the most profound ethical teachers who ever lived.
He was the author-editor of Sefer Chassidim, a profound ethical/halachic treatise which has come down to us in two separate editions. The book has achieved great popularity and has been reprinted many times.
Rav Yehudahs father, Shmuel, was a saintly and renowned Rosh Yeshiva in Speyer, and Rav Yehudah studied under him.
His contemporaries said of him: Had he lived in the times of the prophets, he would have been a prophet; in the time of the tannaim, he would have been a tanna; in the time of the amoraim, an amora ...
Source: Orthodox Union