The 1991 Trans-Tasman Test series was an international rugby league test series played in Australia between Australia and New Zealand. The series, which started on 3 July in Melbourne and finished on 31 July in Brisbane, consisted of three test matches, with the third test doubling as a 1989–1992 Rugby League World Cup tournament match. New Zealand did not play in any other matches while on tour.

The test series was broadcast throughout Australia by the Seven Network with commentary provided by Pat Welsh, Roy Masters and Jon Harker. Paul Vautin provided sideline commentary during the first test in Melbourne but was replaced from the second test by Harker to allow Wally Lewis to join the team following his omission from the Australian test team. Also doing sideline reporting during the series was John Brady. The series was broadcast in New Zealand by TV3 with commentary provided by Australia's Graeme Hughes and former New Zealand and then-Manly-Warringah coach Graham Lowe with sideline comments from former Kiwi test captain Hugh McGahan.

The Australians, coached by Bob Fulton and captained by Mal Meninga, had come out of the successful 1990 Kangaroo Tour, while all players selected for the three Kiwi tests had recently participated in the 1991 State of Origin series, won by Queensland 2–1 over New South Wales (Queensland were actually coached by former Kiwi test coach Graham Lowe). Queensland captain Wally Lewis made his return to the test team for the first test at Olympic Park, after missing most of 1990 and all that year's tests with torn hamstring and later a broken right forearm. Lewis had been controversially ruled out of the Kangaroo Tour by team doctor Nathan Gibbs. Melbourne would prove to be his final test in the Green and Gold, Lewis being one of four players dropped from the side after the 8–24 loss to the Kiwis (second row forward Bob Lindner, voted as the player of the Kangaroo Tour, also missed the final two tests after breaking his leg at Olympic Park).

The series saw the start of the international careers of Canberra Raiders hooker Steve Walters, who beat out Kangaroo incumbent and NSW captain Benny Elias for first test hooking role (Walters had actually been lucky to get the Qld hooking role as his younger brother, former test hooker Kerrod Walters, had been suspended), and wingers Willie Carne (Brisbane Broncos) and Rod Wishart (Illawarra Steelers), who made their debut in the second test in Sydney, with all three scoring tries on debut. Also making his Australian debut in Sydney was Eastern Suburbs front row forward Craig Salvatori, who played his only two career tests during the series. The series would be the last appearance in an Australian jumper of veteran test players Wally Lewis and Des Hasler as well as Penrith forward Mark Geyer. Giant (6 ft 6 in; 198 cm) Broncos and Queensland fullback Paul Hauff, the tallest ever recorded fullback in Australian premiership history, made his only appearance in an Australian jumper in the first test after starring for Qld in the Origin series. It was to be his only test however, with Andrew Ettingshausen preferred for the final two tests.

The New Zealand test team was coached by Bob Bailey and captained by Balmain Tigers halfback Gary Freeman, who had actually been dropped to Reserve Grade at the time by Tigers (and former Wallabies) coach Alan Jones. The Kiwis came into the series on the back of a two-test series win over France, and consisted of players playing in New Zealand, Australia and in the UK, while the Australian team consisted of players only from the Winfield Cup.

Goal kicking former All Blacks and now Wigan-based utility back Frano Botica, who 3 weeks earlier had made his Kiwi debut in the first test against France at Carlaw Park becoming New Zealand's 30th dual rugby international, was the Kiwis fullback for the three tests. Australian coach Bob Fulton rated Botica as good as any fullback in the Winfield Cup. The only Kiwi on debut in Melbourne was Christchurch-born, South Sydney Rabbitohs winger Jason Williams, playing the first of 12 career tests.

The Kiwis were managed by Ray Haffenden. Unlike the Australians whose squad all played in the NSWRL premiership, the Kiwis squad for the tour included those playing in New Zealand, Australia and England. The Kiwis squad was: Gary Freeman (Balmain), Richie Blackmore (Castleford), Frano Botica (Wigan) Peter Brown (Halifax), Clayton Friend (Carlisle), Kevin Iro (Manly-Warringah), Tony Kemp (Newcastle), Emosi Koloto (Widnes), Dean Lonergan (Auckland), Duane Mann (Warrington), George Mann (St. Helens), Jarrod McCracken (Canterbury-Bankstown), Gary Mercer (Warrington), Tawera Nikau (Castleford), Mike Patton (Glenora), Brent Todd (Canberra), Dave Watson (Halifax) and Jason Williams (South Sydney).

Several ex-rugby union players playing in the Winfield Cup, including former All Blacks John Schuster (Newcastle), Matthew Ridge (Manly-Warringah) and Kurt Sherlock (Eastern Suburbs), as well as Daryl Halligan (North Sydney), were unavailable due to a dispute between their respective clubs and the NZRL over compensation, though Manly, Newcastle and the NZRL did manage to come to an agreement over Kevin Iro (who had only joined the Sea Eagles a month before the series) and Tony Kemp respectively. Despite the unavailability of Winfield Cup 'superboots' Ridge and Halligan, the Kiwis lost nothing in goal kicking due to the selection of Wigan 'superboot' Frano Botica.