| OrdanaB2B | B2B | New York City, United States | — | blu.ai |
| OrdercubeOther | Other | Grafing b. München, Germany | — | ordercube.de |
| Orderly HealthB2B | B2B | Denver, United States | — | orderlyhealth.com |
| OrdermarkOther | Other | Los Angeles, United States | Alex Canter | ordermark.com |
| OrderNerdOther | Other | Peachtree Corners, United States | — | ordernerd.com |
| Origami RoboticsIndustrials | Industrials | — | | origami-robotics.com |
| Origami Space DevelopmentB2B | B2B | Berthoud, United States | — | origamispace.com |
| OriginHealthcare | Healthcare | — | Yash Rathod | origin.bio |
| OriginFintech | Fintech | London, United Kingdom | Max Boonen | originmarkets.com |
| OriientOther | Other | Tel Aviv, Israel | Ran Steinfeld | oriient.me |
| Orion FinanceB2B | B2B | Newark, United States | — | orionfinance.ai |
| OrthogonalB2B | B2B | — | | orthogonal.com |
| Osana SaludHealthcare | Healthcare | United States | — | osanasalud.com |
| OtrafyB2B | B2B | Saint Paul, United States | — | otrafy.com |
| OtterSpaceIndustrials | Industrials | Seattle, United States | — | inotterspace.com |
| OTTOConsumer | Consumer | Memphis, United States | — | myotto.net |
| Our Leg UpIndustrials | Industrials | Bundoora, Australia | — | ourlegup.com |
| Outpost BioHealthcare | Healthcare | — | — | outpost.bio |
| OutreachOther | Other | Seattle, United States | Manny Medina | outreach.io |
| OutroveB2B | B2B | San Francisco, United States | | outrove.ai |
| OutverseB2B | B2B | — | — | outverse.com |
| Overdrive HealthHealthcare | Healthcare | — | | overdrive.health |
| OvershootB2B | B2B | — | | overshoot.ai |
| OverstoryOther | Other | Amsterdam, Netherlands | Ton Snelder | 20tree.ai |
| OvertimeConsumer | Consumer | United States | Dan Porter | itsovertime.com |
| Overwatch AIOther | Other | Barcelona, Spain | — | overwatch-ai.com |
| Ovia HealthOther | Other | Boston, United States | Paris Wallace | oviahealth.com |
| OvidaB2B | B2B | Nottingham, United Kingdom | — | ovida.org |
| Owlet Baby CareHealthcare | Healthcare | Lehi, United States | Kurt Workman | owletcare.com |
| Own UpFintech | Fintech | Boston, United States | Patrick Boyaggi | ownup.com |
| OximyB2B | B2B | — | | oximy.com |
| OxusB2B | B2B | — | | oxus-ai.com |
| Ozeki Legal TechnologiesOther | Other | Mill Valley, United States | — | ozeki.ai |
| P.S. Bridal RentalOther | Other | Hertfordshire, United Kingdom | — | psbridal.co.uk |
| PaceB2B | B2B | — | Khaled Helioui | paceup.com |
| Pacific FusionIndustrials | Industrials | — | Michl Binderbauer | pacificfusion.com |
| PackEducation | Education | Firenze, Italy | — | thepack.tech |
| PackworksFintech | Fintech | Makati, Philippines | — | thepackworks.com |
| PadSplitOther | Other | Atlanta, United States | Atticus LeBlanc | padsplit.com |
| PaidFintech | Fintech | Darlington, United Kingdom | — | paid.co.uk |
| PaidB2B | B2B | — | — | paid.co.uk |
| PairB2B | B2B | — | — | pairnow.ai |
| PalaceB2B | B2B | San Francisco, United States | | palace.so |
| PaladinConsumer | Consumer | New York City, United States | Alison Rooney | joinpaladin.com |
| PalantirB2B | B2B | — | Alexander Karp | palantir.com |
| PallyB2B | B2B | San Francisco, United States | | pally.com |
| PalomaB2B | B2B | San Francisco, United States | | getpaloma.ai |
| Palus FinanceFintech | Fintech | — | | palus.finance |
| PanaConsumer | Consumer | Denver, United States | Devon Tivona | pana.com |
| PandiumOther | Other | New York City, United States | Cristina Flaschen | pandium.com |