|Baron Clas Eriksson Fleming|
|1st Lord High Admiral of Sweden|
1571? 1588? – 1591?
|Succeeded by||Axel Nilsson Ryning|
|Lord High Constable of Sweden|
1591? – ?
|Preceded by||Gustaf Olofsson Stenbock|
|Succeeded by||Magnus Brahe|
|1st Governor-General of Finland|
1594 – ?
Pargas, Sweden (now in Finland)
|Died||13 April 1597
Pojo, Sweden (now part of Raseborg in Finland)
Baron Clas Eriksson Fleming (Finnish: Klaus Fleming) (1535, Pargas, Sweden – 13 April 1597, Pohja, Finland was a Finnish-born member of the Swedish nobility and admiral, who played an important role in Finnish and Swedish history during the rise of Sweden as a Great Power. He was a trustee of Swedish kings John III and Sigismund Vasa.
In 1569 Fleming became a member of the Privy Council, in 1571 he was made Lord High Admiral and in 1590 Lord High Constable. As the Governor of Finland and Estonia he carried the duties of the highest authority of Finland and Estonia for the Swedish realm, next only to the king of Sweden. He was a strong supporter of the legitimate king of Sweden Sigismund Vasa and therefore an enemy of Sigismund's paternal uncle, duke Charles of Sudermania, who had also laid claim to the Swedish throne.
Fleming's father – a grandson of Björn Ragvaldsson – was the Councilor of State Erik Fleming (1487–1548), also a remarkable man and King Gustav Vasa's favourite. Fleming's sons were executed in the Åbo Bloodbath of 1599.
When studying Swedish history of the time it is noteworthy to know there were many persons in similar position with the name Clas Fleming at the time. Clas Eriksson Flemming should not be mixed with Claes Larsson Fleming (1592–1644), admiral and advisor to the king, or Klas Fleming (1649–1685), nobleman and politician.
- "Nordisk Familjebok - Riksamiral". Nordisk Familjebok at runeberg.org (in Swedish). 1916. Retrieved 2009-05-14.
- Hofberg, Herman; Heurlin, Millqvist & Rubensson (1906). "Svenskt biografiskt handlexikon - Klas Fleming". Svenskt biografiskt handlexikon at runeberg.org (in Swedish). Retrieved 2009-05-14.