Ashrei (Hebrew: אַשְׁרֵי, lit. 'happy [is]') is a Jewish prayer recited at least three times daily in Judaism: twice during Shacharit (the morning service) and once during Mincha (the afternoon service). The prayer is composed primarily of the entirety of Psalm 145, with Psalm 84:5 and Psalm 144:15 appended to the beginning and Psalm 115:18 to the end, respectively. The first two verses added both begin with the Hebrew word ashrei, which lends the prayer its name.

In Berakhot 4b:16, Rabbi Elazar, citing Rabbi Avina, is recorded teaching that "anyone who recites Tehillah l'David (תְּהִלָּה לְדָוִד, '[a] Praise [to God] of David') three times every day is assured of a place in the World-to-Come". The Tehillah l'David referred to is Psalm 145; the Rabbis—at least as they were recorded teaching in the Talmud—did not refer to the Ashrei of Rabbinic Judaism as Ashrei.

Ashrei is recited three times daily during the full course of Jewish prayers, in accordance with the Talmudic statement that one who recites Ashrei three times daily is guaranteed a place in the World to Come. For this reason, not only is Ashrei recited these three times, but many of its verses occur throughout liturgy.

Ashrei is recited twice during Shacharit (once during Pesukei D'Zimrah and once between Tachanun/Torah reading and Psalm 20/Uva Letzion or in this place when any of these are omitted), and once as the introduction to Mincha; it is also recited in many customs at the commencement of Selichot services. On Yom Kippur, Ashkenazi Jews recite it during Ne'ila instead of during Mincha, whereas Sephardim and Italkim recite it during both Mincha and Ne'ila.

The majority of Ashrei is Psalm 145 in full. Psalm 145 is an alphabetic acrostic of 21 verses, each starting with a different letter of the Hebrew alphabet arranged alphabetically. This makes Ashrei easy to memorize. The only Hebrew letter that does not begin a verse of Psalm 145 is nun (נ). This omission is discussed at greater length in the Wikipedia article on Psalm 145. Although the Septuagint and some other non-Massoretic versions of the Bible have such a line, no Jewish prayerbook inserts a line beginning with nun.

The first two verses are from Psalms 84:4-5 and Psalms 144:15 respectively. The final verse is Psalm 115:18. The Rome liturgy adds to this Psalm 119:1 and Machzor Vitry (12th century) adds four (possibly five) other verses beginning with the same word ("Ashrei") (namely Psalms 119:1-2, 84:6, 112:1, and 89:16), and it appears that originally the general practice was to have more introductory verses than the two now used by Ashkenazic and Sephardic Jews.

It is customary for the congregants to be seated while reciting Ashrei, as the introductory verse, "Happy are the people who dwell in Your house", describes the congregants as part of the household, not strangers or mere visitors, so they sit to demonstrate that connection. The word ישב, here translated as "dwell", also means "sit down" (as in Exodus 17:12, I Kings 2:12, and Psalm 122:5).^{[citation needed]}

Verse 7 (ז): It has been noticed that, while the majority of Hebrew Bibles spell the first word of this verse with a long vowel - זֵכֶר (zaykher), many prayerbooks print this word with a short vowel - זֶכֶר (zekher) -- the two variants being described as "five dots" and "six dots" respectively. There is no difference in meaning, both variants mean the same thing, a "remembrance" or a "reminder", and both occur elsewhere in the Hebrew Bible, although the long vowel form occurs more often.