| Period | Members | Releases |
| December 1975 – October 1976 | Steve Harris – bass, backing vocals Ron Matthews – drums Terry Rance – guitars Dave Sullivan – guitars Paul Mario Day – lead vocals | none – live performances only |
| October 1976 – November 1976 | Steve Harris – bass, backing vocals Ron Matthews – drums Terry Rance – guitars Dave Sullivan – guitars Dennis Wilcock – lead vocals |
| December 1976 – mid-1977 | Steve Harris – bass, backing vocals Ron Matthews – drums Dennis Wilcock – lead vocals Dave Murray – guitars Bob Sawyer (a.k.a. Rob Angelo) – guitars |
| Mid-1977 – November 1977 | Steve Harris – bass, backing vocals Dennis Wilcock – lead vocals Thunderstick – drums Terry Wapram – guitars Tony Moore – keyboards |
| November 1977 – early 1978 | Steve Harris – bass, backing vocals Dennis Wilcock – lead vocals Thunderstick – drums Terry Wapram – guitars | none – rehearsals only |
| March 1978 – April 1978 | Steve Harris – bass, backing vocals Dennis Wilcock – lead vocals Thunderstick – drums Dave Murray – guitars |
| Early 1978 – November 1978 | Steve Harris – bass, backing vocals Dave Murray – guitars Doug Sampson – drums |
| November 1978 – early 1979 | Steve Harris – bass, backing vocals Dave Murray – guitars Doug Sampson – drums Paul Di'Anno – lead vocals Paul Cairns (a.k.a. "Mad Mac") – guitars | The Soundhouse Tapes (1979) |
| June 1979 | Steve Harris – bass, backing vocals Dave Murray – guitars Doug Sampson – drums Paul Di'Anno – lead vocals Paul Todd – guitars | none – rehearsals only |
| September – December 1979 | Steve Harris – bass, backing vocals Dave Murray – guitars Doug Sampson – drums Paul Di'Anno – lead vocals Tony Parsons – guitars | none – live performances only |
| December 1979 – November 1980 | Steve Harris – bass, backing vocals Dave Murray – guitars Paul Di'Anno – lead vocals Clive Burr – drums Dennis Stratton – guitars, backing vocals | Iron Maiden (1980) |
| November 1980 – September 1981 | Steve Harris – bass, backing vocals Dave Murray – guitars Paul Di'Anno – lead vocals Clive Burr – drums Adrian Smith – guitars, backing vocals | Killers (1981) |
| September 1981 – December 1982 | Steve Harris – bass, backing vocals Dave Murray – guitars Clive Burr – drums Adrian Smith – guitars, backing vocals Bruce Dickinson – lead vocals | The Number of the Beast (1982) |
| December 1982 – June 1990 | Steve Harris – bass, backing vocals, synthesisers (1986-1988) Dave Murray – guitars, synthesisers (1986) Adrian Smith – guitars, backing vocals, synthesisers (1986-1988) Bruce Dickinson – lead vocals, additional guitars (1983-1985) Nicko McBrain – drums Michael Kenney – keyboards (touring; 1988-onward) | Piece of Mind (1983) Powerslave (1984) Somewhere in Time (1986) Seventh Son of a Seventh Son (1988) |
| June 1990 – August 1993 | Steve Harris – bass, backing vocals Dave Murray – guitars Bruce Dickinson – lead vocals Nicko McBrain – drums Janick Gers – guitars Michael Kenney – keyboards (touring) | No Prayer for the Dying (1990) Fear of the Dark (1992) |
| January 1994 – January 1999 | Steve Harris – bass, backing vocals, keyboards Dave Murray – guitars Nicko McBrain – drums Janick Gers – guitars Blaze Bayley – lead vocals Michael Kenney – keyboards (touring) | The X Factor (1995) Virtual XI (1998) |
| January 1999 – December 2024 | Steve Harris – bass, backing vocals, keyboards Dave Murray – guitars Nicko McBrain – drums Janick Gers – guitars Adrian Smith – guitars, backing vocals Bruce Dickinson – lead vocals Michael Kenney – keyboards (touring; 1999–2022) Brett Diamond – keyboards (touring; 2022–onwards) | Brave New World (2000) Dance of Death (2003) A Matter of Life and Death (2006) The Final Frontier (2010) The Book of Souls (2015) Senjutsu (2021) |
| December 2024 – present | Steve Harris – bass, backing vocals, keyboards Dave Murray – guitars Nicko McBrain – drums (retired from touring) Janick Gers – guitars Adrian Smith – guitars, backing vocals Bruce Dickinson – lead vocals Simon Dawson – drums (touring) Brett Diamond – keyboards (touring) | |