| 1980s: | 1983 1984 1985 1986 1987 1988 1989 |
| 1990s: | 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 |
| 2000s: | 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 |
| 2010s: | 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 |
| 2020s: | 2020 2021 2022 2023 2024 2025 2026 |
This page contains Sega-related events that occurred in 2003.
Events
- January 8: Relude Oy, later known as Rovio Entertainment is founded.
- February 13: Sega announces it's planned merger with Sammy.
- April 17: Sega still in talks with Namco over mergers. The consideration of the merger with Namco after announcing they will merge with Sammy by Sega upsets Sammy's executives and nearly causes problems.
- Unknown: The day after Sega announces they no longer will be merging with Sammy, Namco withdraws it's offer.
- August: Sammy buys a 22.4% share in Sega
- First entry in the Mushiking and Billy Hatcher series.