TUI fly Deutschland (legally TUIfly GmbH), formerly TUIfly, is a German leisure airline owned by the travel and tourism company TUI Group. It is headquartered at Hannover Airport with bases at several other German airports. TUI fly Deutschland is part of TUI Group's airline unit.

The airline was formed in 2007 by the merger of Hapag-Lloyd Flug and Hapag-Lloyd Express as a branch of TUI Travel. At that time, when the airline began operation after merger, the first aircraft was already repainted into the airline's new name and livery only months before the current airline took its first flight. When the airline began operations, the airline codes from its predecessors are still in use, and the two callsigns YELLOWCAB and HAPAG LLOYD both incorporated from their predecessors was used until it was changed to TUIJET on 24 September 2010 following the merger.^{[citation needed]}

In the second quarter of 2007, the load factor was at about 79%, compared to about 92% the year before. The company closed its Leipzig/Halle and Bremen bases. On 29 January 2008, plans were announced to merge TUIfly with Eurowings and Germanwings (Lufthansa low-cost subsidiaries) to form a joint and independent holding company, but the talks were ultimately unsuccessful.

TUI Travel confirmed on 27 March 2009 that it had signed a strategic partnership with Air Berlin that would see TUI Travel take a 20% stake in Air Berlin, and Air Berlin 20% in TUI fly Germany. Due to regulatory concerns, this was changed to 9.9%. Air Berlin was also to wet-lease 17 aircraft from TUI fly and take over all of TUI fly Germany's city connections. TUI was to focus on serving the charter market with 21 aircraft. From 25 October 2009 onwards, all German domestic flights previously operated by TUI fly Germany were operated by Air Berlin, as well as all flights to Austria, Italy and Croatia. Most of these flights were still operated by TUI fly Germany aircraft, but were marketed by Air Berlin.

In December 2013, TUI fly Deutschland abandoned its distinctive yellow livery after 7 years and replaced it with a blue design which had already been introduced at TUI fly Netherlands, TUI fly Belgium and TUI Airways. The first plane in the new colors arrived in Hannover on 17 February 2014. The livery was updated in 2016, with titles shortened from "TUIfly" to "TUI".

In September 2014, TUI fly Deutschland decided to relocate their operations at Zweibrücken Airport to nearby Saarbrücken Airport as Zweibrücken Airport faced bankruptcy and an uncertain future. In January 2016, TUI fly Deutschland also announced it would leave Hamburg Airport entirely due to the increasing competition from low-cost carriers. The summer seasonal routes did not resume, and all remaining routes ended by March 2016.

In September 2016, plans were announced to merge TUI fly Deutschland with Air Berlin's leisure operations - which were partially operated by TUI fly Germany - as well as Air Berlin's entire Austrian subsidiary Niki. On 5 October 2016, TUI fly Deutschland confirmed it was in talks with Air Berlin and Etihad Airways to create a new holding company for leisure operations. The new company was planned to serve important holiday destinations from Germany, Austria, and Switzerland. In June 2017, TUI Group and Etihad Aviation Group announced that joint venture negotiations had ended.

In July 2018, the airline announced it would close its base at Karlsruhe/Baden-Baden Airport by October 2018.