MoodleDocs:Overview

English

3.1 EN documentation
3.0 EN documentation
2.9 EN documentation
2.7 EN documentation

Also:
Developer documentation

Català (Catalan)

2.x CA documentation
1.9 CA documentation

Deutsch (German)

3.1 DE documentation
3.0 DE documentation
2.9 DE documentation
2.7 DE documentation

Español (Spanish)

ES documentation

Euskara (Basque)

EU documentation

Français (French)

2.x FR documentation
1.9 FR documentation

Hrvatski (Croatian)

HR documentation

Íslenska (Icelandic)

IS documentation

日本語 (Japanese)

2.x JA documentation
1.9 JA documentation

Polski (Polish)

2.x PL documentation

Português Brasileiro (Brazilan Portuguese)

PT_BR documentation

Suomi (Finnish)

FI documentation

中文 (Chinese)

ZH documentation