Catechetical Lectures
- Delivered in 347 or 348 by St. Cyril of Jerusalem. Edwin Hamilton Gifford translation. In HTML, with notes.
- http://www.ccel.org/ccel/schaff/npnf207.ii.html

Catechism of the Catholic Church
- A complete online version of the 1992 Catechism of the Catholic Church. Can be searched by keywords, phrases, or paragraph number. Viewing results in context, however, requires JavaScript.
- http://www.christusrex.org/www1/CDHN/ccc.html

Instructions on the Catechism
- By St. John Vianney. 246K.
- http://www.ewtn.com/library/CATECHSM/CATARS.htm

Baltimore Catechism (1891)
- The Baltimore Catechism, Nos. 1, 2, and 3. Missing Lesson 28 in Catechism No. 3. Has concordances and word frequency lists. Each lesson in its own file. Some scanner errors.
- http://www.intratext.com/X/ENG0104.htm

An Abridgment of the Christian Doctrine
- Also known as the Douay Catechism. By Henry Tuberville. 1833 edition of book originally published in 1649. Complete text. 395K.
- http://www.aloha.net/~mikesch/DouayCat.htm

A Catechisme, or, Christian Doctrine
- By Lawrence Vaux. The first English-language Catholic catechism of the Reformation era. 1583 edition. Online version includes illustrations and preserves pagination, but spelling is modernized. Full text. 207K.
- http://www.aloha.net/~mikesch/vaux.htm

A Catechism of Christian Doctrine
- More popularly known as the Penny Catechism. Full text. 107K.
- http://www.memorare.com/catechism/pennycat.txt

The Baltimore Catechism
- Searchable full text of the Baltimore Catechism, Nos. 1, 2, and 3. Also available for download in Microsoft Word format. Some scanner errors.
- http://www.catholic.net/rcc/Catechism/Doit.html

The Great Catechism
- By St. Gregory of Nyssa. Presupposes familiarity with classical philosophy. Moore-Wilson translation, with summary and notes. 182K.
- http://www.ccel.org/fathers2/NPNF2-05/Npnf2-05-39.htm

The Roman Catechism
- Written after the Council of Trent and containing doctrinal statements arising from the Catholic Reformation. Intended for parish priests. Also called the Catechism of Pius V, or the Catechism of Trent.
- http://www.cin.org/users/james/ebooks/master/trent/tindex.htm

Catechism of St. Pius X
- Pope St. Pius X wrote this simple catechism for use by the faithful. It was used in Italy, but was not given the wider circulation the Holy Father had hoped for. It explains in a simple style the truths of the Faith.
- http://www.cin.org/users/james/ebooks/master/pius/pindex.htm

Baltimore Catechism No. 4
- Also known as "An Explanation of the Baltimore Catechism." Complete text. This version was intended for teachers, that is, for catechists.
- http://www.cin.org/users/james/ebooks/master/baltimore/bindex.htm