| IAO Nr. | Year | Dates | Country | Scientific Center, Observatory or Institute |
Town | Time Zone | Number of states | Lo- cal te- am ** |
|
| partici- pating |
obser- ving |
||||||||
| Preliminary | 1990 | October 20-22 |
Moscow Land * |
NSC RAS, ISSP RAS |
Chernogolovka | UT+04 | 3 | 1 | + |
| Preliminary | 1991 | December 13-16 |
Moscow Land * |
NSC RAS, ISSP RAS |
Chernogolovka | UT+02 | 4 | 1 | + |
| I IAO | 1996 | November 1-9 |
Russia | SAO RAS | Nizhnij Arkhyz | UT+03 | 4 | 1 | - |
| II IAO | 1997 | October 21-28 |
Russia | SAO RAS | Nizhnij Arkhyz | UT+04 - UT+03 | 4 | - | - |
| III IAO | 1998 | October 20-27 |
Russia | SAO RAS | Nizhnij Arkhyz | UT+04 - UT+03 | 5 | 1 | - |
| IV IAO | 1999 | September 25 - October 2 |
Crimea * | CrLab SAI, CrAO |
Nauchnyj | UT+03 | 7 | 2 | - |
| V IAO | 2000 | October 20-27 |
Russia | SAO RAS | Nizhnij Arkhyz | UT+04 | 8 | - | - |
| VI IAO | 2001 | September 26 - October 3 |
Crimea * | CrLab SAI, CrAO |
Nauchnyj | UT+03 | 7 | 1 | - |
| VII IAO | 2002 | October 22-29 |
Russia | SAO RAS | Nizhnij Arkhyz | UT+04 - UT+03 | 11 | - | + |
| VIII IAO | 2003 | October 3-8 |
Sweden | Stockholm Observatory | Stockholm | UT+02 | 13 | 2 | + |
| IX IAO | 2004 | October 1-9 |
Crimea * | CrLab SAI, CrAO |
Simeiz | UT+03 | 18 | - | - |
| X IAO | 2005 | October 25 - November 2 |
China | Beijing Planetaruim | Beijing | UT+08 | 15 | 2 | + |
| XI IAO | 2006 | November 10-19 |
India | TIFR | Bombay ( Mumbai ) |
UT+0530 | 16 | 3 | n o r u l e * n o r u l e * n o r u l e * n o r u l e |
| XII IAO | 2007 | September 29 - October 7 |
Crimea * | CrLab SAI, CrAO |
Simeiz | UT+03 | 23 | 1 | |
| XIII IAO | 2008 | October 13-21 |
Italy | Trieste Astronomical Observatory | Trieste | UT+02 | 19 | - | |
| XIV IAO | 2009 | November 8-16 |
China | Beijing Planetaruim | Hangzhou | UT+08 | 17 | 1 | |
| XV IAO | 2010 | October 16-24 |
Crimea * | CrLab SAI, CrAO |
Sudak | UT+03 | 19 | - | |
| XVI IAO | 2011 | September 22-30 |
Kazakhstan | AFI | Alma-Ata | UT+06 | 19 | 2 | |
| XVII IAO | 2012 | October 16-24 |
Korea | SNU | Gwangju | UT+09 | 20 | 2 | |
| XVIII IAO | 2013 | September 6-14 |
Lithuania | Vilnius University Observatory | Vilnius | UT+03 | 20 | - | |
| XIX IAO | 2014 | October 12-21 |
Kyrgyzstan | AFI | Bishkek - Cholpon-Ata |
UT+06 | 17 | - | |
| XX IAO | 2015 | October 15-23 |
Russia | Kazan University Observatory | Kazan | UT+03 | 13 | - | |
| XXI IAO | 2016 | October 5-13 |
Bulgaria | Rozhen Observatory | Pamporovo - Smolyan |
UT+03 | 16 | - | |
| XXII IAO | 2017 | October 27 - November 4 |
China | Weihai University | Weihai | UT+08 | 13 | 2 | |
| XXIII IAO | 2018 | October 6-14 |
Sri Lanka | Colombo University | Colombo | UT+0530 | 19 | - | |
| XXIV IAO | 2019 | October 19-27 |
Romania | Piatra Neamt | UT+03 - UT+02 | 20 | - | ||
| XXV IAO - I IRAO | 2021 | November 5-13 |
Italy | INAF | Milan | UT+01 | |||
| XXVI IAO - II IRAO | 2022 | October 15-24 |
Italy | INAF | Matera | UT+02 | |||
| XXVII IAO | 2023 | November 6-14 |
China | Beijing Planetaruim | Beijing | UT+08 | |||
| XXVIII IAO - III IRAO | 2024 | December 8-17 |
Bangladesh | East-West University | Cox's Bazar | UT+06 | |||
| XXIX IAO - IV IRAO | 2025 | November 6-18 |
Bangladesh | East-West University | Dhaka | UT+06 | |||
| XXX IAO | 2026 | early December | Uzbekistan | Andizhan | UT+05 | ||||
(*) Moscow Land and Peninsula of Crimea, as organizers of the oldest open astronomical Olympiads/competitions (have existed for more than 50 years), and due to their historical service in the formation and development of IAO, they are considered as independent states with all rights and duties. Both Moscow Land and Crimea are geographical terms and have no any administrative or political meaning.
(**) Till 2005, the host team had right to participate at the IAO as an additional team in the case of fulfilling some special requirements. Thus, there were participated: team of NSC RAS at the preliminary Olympiads, team of SAO RAS at the VII IAO, team of Stockholm city at the VIII IAO, and team of Beijing city/province at the X IAO. Starting in 2006, this right was redirected to APAO.