Although Calvin's Institutes are better known, it is his commentaries which lay the foundation for all that is presented in the Institutes.
This 45 volume set was translated, and published, by the Calvin Translation Society (who also published the original version of Beveridge's translation of the Institutes). First published in the 1840s and 1850s, they have remained in print since that time.
Not every book of the Bible is covered but those that are always reward careful study. And even if, finally, you do not agree with Calvin's conclusions, the care with which he exegetes will earn your respect.
Follow the link above for the online version of Calvin's Commentaries. If you want to download them follow the links below to Internet Archive.
Please note that for some volumes the description on the Internet Archive page is not correct. Also volume numbers may be inaccurate.
Joshua: Volume 7. [This volume also includes a dissertation by Tholuck on "Calvin as an interpreter of the Holy Scriptures".]
Hosea: Volume 26. [This volume includes a portrait of Calvin from Beza's Icones.]
Joel, Amos, Obadiah: Volume 27.
Jonah, Micah, Nahum: Volume 28.
Habakkuk, Zephaniah, Haggai: Volume 29.
Zecharaiah, Malachi: Volume 30.
Galatians, Ephesians: Volume 41.
Philippians, Colossians, Thessalonians: Volume 42. [This volume includes Four Sermons on Idolatry, and an Exposition of Psalm 87.]
Timothy, Titus, Philemon: Volume 43.
Hebrews: Volume 44.
James, 1 & 2 Peter, Jude, 1 John: Volume 45.
If you are interested in earlier translations of the commentaries into English then there is an edition of Genesis published in 1578, and an edition of Isaiah published in 1609, a Harmony of the Gospels plus the Gospel of John published in 1610, and an edition of James published in 1797.