The German duo were integral to last season's success as the club returned to the top-flight of English football for the first time in 45 years.
Signing from 1. FC Kaiserslautern last summer, Lowe went on to make the left-back slot his own during the triumphant SkyBet Championship campaign.
Although he had two years left on his current contract, the new deal now runs until June 30, 2020 with Town having an option on a further year's extension at that point.
Meanwhile, Kachunga has also signed an improved deal after a stunning debut season witnessed the DR Congo forward top the club's scoring charts.
Joining the club initially on loan from German side FC Ingolstadt, the forward made the move permanent in March with today's new deal seeing him remain at the club until 2020 and with an option of a further year's extension.
On the new deals, Huddersfield Town Head Coach David Wagner said: “It’s very important that Chris and Elias have committed their futures to Huddersfield Town by signing new contracts.
“Both Chris and ‘Kache’ were big players for the team as we gained promotion to the Premier League last season.
“I knew they were both high quality footballers when they arrived, but they deserve so much credit for the way they adapted to English football so quickly.
“That is testament to their characters and personalities as much as their footballing ability.
“They will continue to be big, big players for us in the Premier League season and these new contracts are also a reward for what they have achieved with us so far.
“I expect that more of the players who have made this journey into the Premier League will also commit their futures to the club in the coming weeks.”