The 18-year-old, who can play either as a centre-back or as a defensive midfielder, featured just five times last season under former Blues boss Maurizio Sarri.
New Chelsea manager Frank Lampard revealed recently he tried to sign Ampadu on loan in January when he was in charge at Derby.
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The move to RB Leipzig will be Ampadu’s first loan spell since his arrival at Stamford Bridge from Exeter two years ago.
Ampadu has made 12 appearances in his two years with Chelsea and in September 2018 he signed a new five-year contract.
Chelsea are banned from signing players during the next two transfer windows until the end of January 2020, which could have opened up an opportunity for Wales international Ampadu this season.