Psalm 122 is the 122nd psalm of the Book of Psalms, beginning in English in the King James Version: "I was glad" and in Latin entitled Laetatus sum. It is attributed to King David and one of the fifteen psalms described as A song of ascents (Shir Hama'alot). Its title, I was glad, is reflected in a number of choral introits by various composers.

In the slightly different numbering system used in the Greek Septuagint and Latin Vulgate translations of the Bible, this psalm is Psalm 121.

The psalm is attributed to King David; however, Alexander Kirkpatrick suggests that its author lived "in the country, at a distance from Jerusalem. He recalls the joy with which he heard the invitation of his neighbours to join the company of pilgrims". He adds, "the psalm may best be explained thus, as the meditation of a pilgrim who, after returning to the quiet of his home, reflects upon the happy memories of his pilgrimage."

Psalm 122 is recited in some communities following Mincha between Sukkot and Shabbat Hagadol. It is also recited on Shabbat Nachamu (the Shabbat after Tisha B'Av) in some traditions.

It is recited on Yom Yerushalayim in the Conservative Jewish tradition due to the psalmist speaking of a united Jerusalem.

Verses 7–9 are cited in Talmud Brachos 64a, which has been incorporated into various parts of the liturgy.

According to the Rule of St. Benedict, this Psalm was to be recited during the third act of the week, that is to say on Tuesday through Saturday, after Psalm 120 (119) and Psalm 121 (120).

In the Liturgy of the Hours in general use today, Psalm 122 is recited or sung at Vespers on the Saturday of the fourth week of the four-week cycle. It is also used at Second Vespers in the Common texts for the feasts of both the Blessed Virgin Mary and of all Holy Women.