The TARDIS (abbreviation for Time And Relative Dimension(s) In Space) was a type of spacecraft and time machine, one of which was utilized by the Guardian Captain Lewis. (Star Trek: Unity). It is most often seen resembling a British Police Box.

In 2387, the TARDIS was discovered by Captain Puto and Captain Lewis on Iconia during their search for the Elementux device. Upon entering the box, the pair were transported by the pre-programmed time machine first to Earth in 2008 where they collected an ancient fob watch as well as new friends Becky & Jade, then to the planet Exo III. There, Lewis subsequently adopted his previous persona of "The Doctor" from looking into the fob watch, and he took possession of the TARDIS, which was then kept on board the USS Odyssey-A, hidden from Starfleet's knowledge. At the conclusion of the Time War in 2389, Lewis used the time machine to return his crew, including Laura Lee and his regenerated clone to their proper times, before leaving the machine on Unity Starbase. (Star Trek: Unity)

In an alternate 2360s, another TARDIS is utilised by Devoid & Sally Sillington prior to them joining the Unreliable. The ship was kept aboard the Unreliable, initially on the bridge before being transferred to the shuttlebay sometime after 2364. The ship was used by Sally SIllington to rescue Devoid, Breezie & Sutaba from the NX-02 after Devoid was attacked and knocked unconcious. (The Unreliable's Light)