Microsoft does directly host some Office 2013 SP1 Language Pack executables — these are official, verifiable, and safe.
Example direct URL pattern (English):
https://download.microsoft.com/download/3/D/6/3D66A460-79D8-452F-BC65-891761A5E766/officesp2013langpacken-us.exe
For other languages, change the ending:
Base path (same for all):
https://download.microsoft.com/download/3/D/6/3D66A460-79D8-452F-BC65-891761A5E766/
Microsoft may remove or change URLs; if a link fails, search Microsoft Update Catalog or Microsoft Download Center for "Office 2013 Language Pack" and the language plus bitness. microsoft office 2013 language pack direct link top
Related search suggestions provided.
32-bit Direct Link
64-bit Direct Link
For enterprise users holding a Volume License agreement, direct downloads are still available, though they are not "public" links.
If you have a legitimate Volume License for Office 2013 Professional Plus, log into the VLSC. This is the absolute safest top source for every language, including rare ones like Basque, Galician, or Uzbek. Search for “Office 2013 Language Pack” – you will find ISO files containing all 40+ languages. Microsoft does directly host some Office 2013 SP1
Below are the direct links for the most requested languages. These are .exe or .img files that you can run immediately.