- Alphabet (the main company)
- B (possibly Boston Dynamics, but whether it's remaining under Google is unclear at this point)
- Calico (focused on longevity)
- Capital (investment)
- D
- E
- Fiber
- Google (now led by Sundar Pichai and includes search, ads, maps, apps, YouTube, and Android)
- Hooli
- I
- J
- K
- Life Sciences ("that works on the glucose-sensing contact lens")
- M
- Nest
- O
- P
- Q
- R
- S
- T
- U
- Ventures (investment)
- W
- X lab ("which incubates new efforts like Wing, our drone delivery effort")
- Y
- Z
If you want to suggest other companies that Google can buy to complete its alphabet, comments are open.