In the March 2018 Legislative Council by-elections for the four seats left vacant by the disqualified legislators over the oath-taking controversy, three candidates were disqualified by the Electoral Affairs Commission (EAC) returning officers, including Demosistō's Agnes Chow on the basis of that she "cannot possibly comply with the requirements of the relevant electoral laws, since advocating or promoting 'self-determination' is contrary to the content of the declaration that the law requires a candidate to make to uphold the Basic Law and pledge allegiance to the [Hong Kong Special Administrative Region]".
In a company public announcement on March 15, 2018, Parker said Trevor Edwards, a top Nike executive who was seen as a potential successor to the chief executive, was relinquishing his position as Nike's brand president and would retire in August.
With her improved ranking, Kenin was able to play primarily on the WTA Tour in 2018. She began the year by reaching her first WTA quarterfinal at the Auckland Open. After losing her first-round match at the Australian Open, Kenin produced good results at both Premier Mandatory events in March. She entered the top 100 by reaching the second round of the Indian Wells Open as a qualifier. She then qualified for and reached the third round of the Miami Open, where she upset No. 11 Daria Kasatkina.
Facebook customer Global Science Research sold information on over 87 million Facebook users to Cambridge Analytica, a political data analysis firm. According to The Guardian both Facebook and Cambridge Analytica threatened to sue the newspaper if it published the story. After publication, Facebook claimed that it had been "lied to". On March 23, 2018, The English High Court granted an application by the Information Commissioner's Office for a warrant to search Cambridge Analytica's London offices, ending a standoff between Facebook and the Information Commissioner over responsibility.
On March 26, the Federal Trade Commission opened an investigation into the matter. The controversy led Facebook to end its partnerships with data brokers who aid advertisers in targeting users.
On 31 March 2018, Immobile scored twice in Lazio's 6–2 home win over Benevento, his 36th goal of the season, breaking Giorgio Chinaglia's previous record for most goals scored by a Lazio player in a single season, by two goals.