The 21-year-old Belgian joined Watford from Anderlecht in January 2018 and was a substitute in a 2-0 Premier League defeat at West Ham the following month.

He spent last season on loan with Bundesliga side Fortuna Dusseldorf, scoring 14 goals in 34 games.

That included a hat-trick in a 3-3 draw with Bayern Munich in November.

The Belgium Under-21 international is the only player to ever score three goals in a Bundesliga game against Manuel Neuer.

"Hertha is a big club in Germany and showed a lot of interest in me," said Lukebakio after signing what his new club call a long-term deal.

"I knew very quickly that I wanted to join the club. I want to play a lot of football here and score loads of goals."