According to Sky, Dortmund have identified the 18-year-old attacking midfielder as a potential addition, while Bayern are also interested in the teenager.
Chelsea, Manchester City and Manchester United are understood to be monitoring Williams-Barnett as well, giving Tottenham significant competition for his signature.
The youngster remains under contract with Spurs until 2028 but is reportedly open to leaving the club as he looks for greater opportunities at senior level.
Williams-Barnett made his Tottenham debut in September 2025 but has made only one further first-team appearance since then.
His lack of senior football contrasts sharply with his record in the club’s youth sides, where he has produced impressive numbers.
The attacking midfielder registered 37 goal contributions in 32 appearances for Tottenham Under-18s and added 15 in 12 matches for the Under-21s.
He has also impressed in the UEFA Youth League, scoring seven goals and providing two assists in six appearances.
His vision and finishing have been highlighted as two of his strongest qualities, helping explain why so many leading clubs are monitoring his situation.
Borussia Dortmund have developed a strong reputation for giving young players opportunities to establish themselves at senior level, with Jadon Sancho and Jude Bellingham among the recent examples of English youngsters who flourished in Germany.
Bayern Munich have also shown a willingness to recruit highly rated young talent, meaning Williams-Barnett could have several attractive options if he decides to leave north London.
Tottenham will nevertheless be reluctant to lose a player they have developed through their academy, particularly while he remains under contract for another two years.
The level of interest means his situation is likely to attract increasing attention, especially if his first-team opportunities remain limited.
For now, Williams-Barnett remains a Tottenham player, but the competition from Dortmund, Bayern and three major Premier League clubs could make his future one to watch.