The 2018 Australian ball-tampering scandal, also known as Sandpapergate, was a cricket cheating scandal surrounding the Australian national cricket team. In March 2018, during the third Test match against South Africa at Newlands in Cape Town, Cameron Bancroft was caught by television cameras trying to rough up one side of the ball with sandpaper to make it swing in flight. Captain Steve Smith and vice-captain David Warner were found to be involved and both received unprecedented sanctions from Cricket Australia. Although he was found not to have been directly involved, Australia's coach, Darren Lehmann, announced he would step down from his role following the scandal. Smith was replaced by Tim Paine as captain in all formats before Aaron Finch took over from Paine in ODIs and T20Is.

In March 2018, the Australia national cricket team toured South Africa to play four Test matches against the South Africa national cricket team. Entering the third Test, the series was level 1–1. On 24 March 2018, during the third day of the third Test, after the 43rd over of South Africa's second innings, Australia's Cameron Bancroft was shown on the television coverage and on screens at the ground appearing to rub the ball with a small yellow object. After Bancroft realised that he had been seen, he was again shown on the television coverage and on screens at the ground hiding the object in the front of his trousers. He was then approached by the umpires and he showed them a dark microfibre sunglass pouch from his pocket. The umpires inspected the ball and chose neither to offer the ball to the South African team to replace it if they wished, nor award them five penalty runs, the options available to the umpires under Law 41.3 of the Laws of Cricket. This indicated that the ball had not been altered in any noticeable way. At the time, South Africa was 129/2 with a 185 run lead.

At the press conference at the end of the day's play, Bancroft, accompanied by Australia's captain, Steve Smith, admitted that he was shown attempting to alter the condition of the ball using a short length of yellow adhesive tape to which dirt and grit had adhered, forming an abrasive surface. Five days later, and after an investigation into the incident by Cricket Australia, he admitted it was sandpaper, which cricketers use to maintain their bats. Smith also admitted that he knew of the plan in advance of Bancroft's actions. Smith said that the plan was made during the lunch break by the "leadership group", which he did not name. Smith said it was a "big mistake", and when questioned by the media, said that he would not be standing down as captain of the team.

Andy Pycroft, the match referee, charged Bancroft with a Level 2 offence of attempting to alter the condition of the ball. David Richardson, CEO of the International Cricket Council (ICC), charged Smith with "conduct of a serious nature that is contrary to the spirit of the game". Smith accepted the charge and the proposed sanction of two suspension points, which equated to a ban for the next Test match, four demerit points being added to his record, and was fined 100% of his match fee. Bancroft accepted the charge against him, was handed three demerit points and fined 75% of his match fee.

Following Smith's admission, Australia's Prime Minister at that time, Malcolm Turnbull, said it was a "shocking disappointment". He phoned Cricket Australia (CA) Board chairman David Peever directly to express that disappointment and concern, saying that there has to be the strongest action taken. The Australian Sports Commission requested that Smith stand down immediately, and the incident was widely condemned by former international players and officials.

In a press release dated 25 March 2018, CA CEO James Sutherland apologised to fans and confirmed that both Smith and Warner had agreed to stand down from their roles of captain and vice-captain respectively for the remainder of the match. In the same release, David Peever announced that Tim Paine, the team's wicket-keeper, had been endorsed by the Board of CA to step in as acting captain, and Smith and Warner would take to the field under him. South Africa went on to win the Test match by 322 runs with Australia dismissed for 107 in the fourth innings.

Cricket Australia launched its own investigation into the incident, led by Executive General Manager Team Performance, Pat Howard, with CA Senior Legal Counsel and Head of Integrity Iain Roy. CA CEO James Sutherland joined the investigators in South Africa. On 27 March 2018, before the findings of that investigation were handed down, opening batsman Matt Renshaw was recalled to the squad from Australia ahead of the fourth Test.

On 27 March 2018, Sutherland announced that as a result of the preliminary investigation Smith, Warner and Bancroft had been charged with bringing the game into disrepute, suspended and would be sent home. He said that further sanctions against the three players would be announced within 24 hours, and that CA was satisfied that no one else was involved. He added that as well as Renshaw, opening batsman Joe Burns and all-rounder Glenn Maxwell were added to the squad to replace them, and confirmed that Paine had been appointed captain for the fourth Test. There was no announcement about the vacant vice-captain position. South Africa dominated the fourth Test against the depleted Australian team, winning by 492 runs to inflict Australia's second heaviest defeat by runs, and winning the series 3–1.