Year 1604 (MDCIV) was a leap year starting on Thursday (link will display the full calendar) of the Gregorian calendar and a leap year starting on Sunday of the 10-day slower Julian calendar.
- The Sikh Holy Scripture Guru Granth Sahib is compiled and edited by Guru Arjan.
- France begins settling Acadia, first successful French North American colony.
- France begins settling French Guiana.
- England concludes the Treaty of London with Spain, ending its involvement in the Eighty Years' War.
- Za Dengel is deposed as Emperor of Ethiopia by Za Sellase, who restores his cousin Yaqob.
- The Table Alphabeticall, the first known English dictionary to be organized by alphabetical ordering, is published.
- Before 1 October, Huntingdon Beaumont completes the Wollaton Wagonway, built to transport coal from the mines at Strelley to Wollaton just west of Nottingham, England. This is currently the world's oldest wagonway with provenance. The exact date is unknown, but a surviving account book for the year ended 30 September 1604 proves it was built within the preceding 12 months.
- The A-text of Christopher Marlowe's The Tragical History of Doctor Faustus is officially published.
- Lancelot de Casteau's L'Ouverture de cuisine published in Liège, including the first printed recipe for choux pastry.
- January 4 – Jakob Balde, German Latinist (d. 1668)
- March 10? – Johann Rudolf Glauber, German-Dutch alchemist and chemist (d. 1670)
- April 5 – Charles IV, Duke of Lorraine (d. 1675)
- May 10 – Jean Mairet, French dramatist (d. 1686)
- June 17 – John Maurice of Nassau, count of Nassau-Siegen (d. 1679)
- August 3 – John Eliot, English puritan missionary (d. 1690)
- August 4 – François Hédelin, abbé d'Aubignac, French author (d. 1676)
- August 12 – Tokugawa Iemitsu, Japanese shogun (d. 1651)
- August 16 – Bernhard of Saxe-Weimar, general in the Thirty Years' War (d. 1639)
- September 13 – William Brereton, English soldier and politician (d. 1661)
- October 14 – Nils Brahe, Swedish soldier (d. 1632)
- November – Jasper Mayne, English dramatist (d. 1672)
- November 3 – Osman II, Sultan of the Ottoman Empire (d. 1622)
- date unknown
- February 29 – John Whitgift, Archbishop of Canterbury (b. 1530)
- March 4 – Fausto Paolo Sozzini, Italian theologian (b. 1539)
- March 13 – Arnaud d'Ossat, French diplomat and writer (b. 1537)
- May 5 – Claudio Merulo, Italian composer (b. 1533)
- June 24 – Edward de Vere, 17th Earl of Oxford, Lord Great Chamberlain of England, poet and possibly playwright (b. 1550)
- August 3 – Bernardino de Mendoza, Spanish military commander
- August 8 – Horio Tadauji, Japanese warlord (b. 1578)
- September 10 – William Morgan, Welsh Bible translator (b. 1545)
- October 18 – Igram van Achelen, Dutch statesman (b. 1528)
- December 3 – George Hastings, 4th Earl of Huntingdon (b. 1540)
- December 22 – Kuroda Yoshitaka, Japanese Daimyo (b. 1546)
- date unknown