Answers.Body: <p><strong>Summary</strong>: </p>
  
  <p>Cesar Munoz from Ecuador is the last untitled player to beat Fischer, in 1961. Kovacevic is the last non-grandmaster to do that in 1970, but obviously he was already very strong. Janosevic in 1967 was a grandmaster but not the most famous of them. And Spassky in 1992 was not <em>that</em> strong anymore...</p>
  
  <p><strong>Detailed answer</strong>:</p>
  
  <p>From 1960 onwards, Bobby Fischer lost 100 chess games that are registered <a href="http://www.chessgames.com/perl/chess.pl?yearcomp=ge&amp;year=1960&amp;playercomp=either&amp;pid=19233&amp;player=&amp;pid2=&amp;player2=&amp;movescomp=exactly&amp;moves=&amp;opening=&amp;eco=&amp;result=2nd" rel="nofollow noreferrer">here</a>.</p>
  
  <p>You can browse this list to pick whom you consider "the weakest" winner. About a half of the games were played in simultaneous displays so they don't qualify as <em>tournament or match game</em>s. The answer might also depends whether you include blitz and rapid tournaments.</p>
  
  <p>Fischer lost a couple of games to non-grandmasters in 1960 (<a href="http://www.chessgames.com/perl/chessgame?gid=1044531" rel="nofollow noreferrer">IM Bernardo Wexler</a>) and 1961 (<a href="http://www.chessgames.com/perl/chessgame?gid=1044124" rel="nofollow noreferrer">Cesar Munoz</a>, <a href="https://en.wikipedia.org/wiki/C%C3%A9sar_Mu%C3%B1oz" rel="nofollow noreferrer"><em>The unknown Ecuadorian caused a sensation in the preliminaries of the Leipzig Olympiad when he beat Bobby Fischer.</em></a>), but if we limit ourselves to 1963 onwards, my suggested answer would be <a href="http://www.chessgames.com/perl/chessgame?gid=1044632" rel="nofollow noreferrer">Dragoljub Janosevic</a> in Skopje, 1967. It seems any other person who beat Fischer after 1963 was a world-class grandmaster (technically Kovacevic was still an IM in 1970 when he beat Bobby Fischer in Bled, but he was already of GM-strength).</p>
  
  <p>Since <a href="https://en.wikipedia.org/wiki/Dragoljub_Jano%C5%A1evi%C4%87" rel="nofollow noreferrer">Janosevic</a> was a (less famous) grandmaster not far from his peak in 1967 who also won games against Tal, Petrosian, Larsen, Bronstein and an aging Botvinnik, there is also an argument to be made that the weakest person to beat the mature Fischer would actually be former world champion Boris Spassky in Belgrade, 1992, when his level of play had already gone down.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2018-01-19T09:52:01.763Z
Answers.LastActivityDate: 2019-12-26T16:11:38.880Z
Answers.LastEditDate: 2019-12-26T16:11:38.880Z
Answers.UserDisplayName: Evargalo
Body: <p>Who was the weakest player to ever beat the mature Bobby Fischer in a tournament or match game? I understand that it's a bit hard to define the "mature" Fischer indeed, since he was incredibly strong even as a teenager, but I mean roughly, let's say, from the early 1960s on, e.g. not counting his very early years. </p>
  
Comments.ContentLicense: CC BY-SA 3.0
Comments.CreationDate: 2018-01-19T09:47:43.770Z
Comments.Text: To have a relatively objective measurement, we could define "weakest" by "lowest Elo-rating". Alas, Elo rating has only been introduced by Fide in 1970, two years before Fischer retired. You also have to precise if you are only interested in long time-control competition games, or if tournament blitz or tournament rapid games are included. Depending on how you precise your question, a possible answer could be Boris Spassky in 1992.
Comments.UserDisplayName: Evargalo
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2019-12-26T16:53:59.903Z
Comments.Text: In 1957 Bobby Fischer lost a tournament game to a player so weak that I've beaten him. But I don't think that counts as "mature" Fischer.
Comments.UserDisplayName: bof
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2019-12-26T20:10:55.540Z
Comments.Text: In 1957 he was 14 or so...
Comments.UserDisplayName: A. N. Other
Tags: <tournament><fischer>
Title: Weakest player to ever beat the mature Bobby Fischer?
ThreadText: # Weakest player to ever beat the mature Bobby Fischer?
  
  (Asked by: username_0 on 2018-01-18)
  
  Who was the weakest player to ever beat the mature Bobby Fischer in a tournament or match game? I understand that it's a bit hard to define the "mature" Fischer indeed, since he was incredibly strong even as a teenager, but I mean roughly, let's say, from the early 1960s on, e.g. not counting his very early years.
  
  **Tags:** tournament, fischer
  
  > **Comments:**
  > **username_1**: To have a relatively objective measurement, we could define "weakest" by "lowest Elo-rating". Alas, Elo rating has only been introduced by Fide in 1970, two years before Fischer retired. You also have to precise if you are only interested in long time-control competition games, or if tournament blitz or tournament rapid games are included. Depending on how you precise your question, a possible answer could be Boris Spassky in 1992.  
  > **username_2**: In 1957 Bobby Fischer lost a tournament game to a player so weak that I've beaten him. But I don't think that counts as "mature" Fischer.  
  > **username_0**: In 1957 he was 14 or so...  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_1 on 2018-01-19. Score: 9 | Accepted answer
  
  **Summary**:
  
  Cesar Munoz from Ecuador is the last untitled player to beat Fischer, in 1961. Kovacevic is the last non-grandmaster to do that in 1970, but obviously he was already very strong. Janosevic in 1967 was a grandmaster but not the most famous of them. And Spassky in 1992 was not *that* strong anymore...
  
  **Detailed answer**:
  
  From 1960 onwards, Bobby Fischer lost 100 chess games that are registered [here](http://www.chessgames.com/perl/chess.pl?yearcomp=ge&year=1960&playercomp=either&pid=19233&player=&pid2=&player2=&movescomp=exactly&moves=&opening=&eco=&result=2nd).
  
  You can browse this list to pick whom you consider "the weakest" winner. About a half of the games were played in simultaneous displays so they don't qualify as *tournament or match game*s. The answer might also depends whether you include blitz and rapid tournaments.
  
  Fischer lost a couple of games to non-grandmasters in 1960 ([IM Bernardo Wexler](http://www.chessgames.com/perl/chessgame?gid=1044531)) and 1961 ([Cesar Munoz](http://www.chessgames.com/perl/chessgame?gid=1044124), [*The unknown Ecuadorian caused a sensation in the preliminaries of the Leipzig Olympiad when he beat Bobby Fischer.*](https://en.wikipedia.org/wiki/C%C3%A9sar_Mu%C3%B1oz)), but if we limit ourselves to 1963 onwards, my suggested answer would be [Dragoljub Janosevic](http://www.chessgames.com/perl/chessgame?gid=1044632) in Skopje, 1967. It seems any other person who beat Fischer after 1963 was a world-class grandmaster (technically Kovacevic was still an IM in 1970 when he beat Bobby Fischer in Bled, but he was already of GM-strength).
  
  Since [Janosevic](https://en.wikipedia.org/wiki/Dragoljub_Jano%C5%A1evi%C4%87) was a (less famous) grandmaster not far from his peak in 1967 who also won games against Tal, Petrosian, Larsen, Bronstein and an aging Botvinnik, there is also an argument to be made that the weakest person to beat the mature Fischer would actually be former world champion Boris Spassky in Belgrade, 1992, when his level of play had already gone down.
  
  
  ---
  
  