William MacIver (/məˈkaɪvər/; born October 28, 1996) is an American professional baseball catcher in the Athletics organization.

[4][5] He did not play in a game in 2020 due to the cancellation of the minor league season because of the COVID-19 pandemic, but was later assigned to the Rockies' alternate training site.

[9] He split the 2022 season between Double-A Hartford and the Triple-A Albuquerque Isotopes, slashing a cumulative .226/.309/.398 with 15 home runs, 50 RBI, and 10 stolen bases.

[10] In 62 total games split between Albuquerque and the rookie–level Arizona Complex League Rockies, he slashed .272/.416/.416 with three home runs, 34 RBI, and 16 stolen bases.

MacIver spent the entirety of the 2024 campaign with Triple–A Albuquerque, playing in 89 games and batting .297/.382/.530 with 15 home runs, 56 RBI, and nine stolen bases.