Directory

Optiver

CorporateFinanceVCForeign

Technology, quantitative research and trading expertise come together to solve complex market challenges and improve financial markets. Explore careers across trading, engineering and quantitative research.

Opto Health

StartupBiotech & Life SciencesConsumerBritish

Digital triage platform that directs patients to the appropriate level of urgent and emergency care via symptom assessment. An MHRA-registered UKCA Class I medical device, it covers 400+ conditions in multiple languages and integrates with NHS Spine and Trust clinical systems.

Optro

CorporateSaaSCybersecurityForeign

Transform how you manage risk with Optro (formerly AuditBoard). The AI-powered GRC platform trusted by over 50% of the Fortune 500. Learn more.

Ora Global

VCDefenceLogisticsForeign

A resilience and defence VC backing founders relentless in their pursuit of building brilliant companies.

Oracle

CorporateSaaSAIForeign

Oracle Corporation is one of the world's largest enterprise technology companies, providing cloud infrastructure, database software, enterprise resource planning, and cloud applications to businesses globally. Its flagship products include the Oracle Database and Oracle Cloud Infrastructure (OCI). The company relocated its corporate headquarters from Redwood City, California to Austin, Texas in 2020.

OrbiSky Systems

StartupSpaceAIBritish

Space assurance company building mission evidence infrastructure for autonomous in-orbit manufacturing, ISAM operations, hosted payload verification and anomaly-aware telemetry review. Awarded a UK Space Agency contract in 2026 to define end-to-end payload verification for in-orbit manufacturing.

Orbital

ScaleupAIProptechForeign

AI platform for real estate law that automates property due diligence, title review and document-heavy legal workflows across the US and UK. Raised a $60 million Series B in January 2026 and supports more than 200,000 real estate transactions annually. Formerly known as Orbital Witness.

Orbital Industries

ScaleupAIClimateBritish

Uses frontier AI and simulation to discover and engineer advanced materials for industrial applications, starting with high-density cooling solutions for GPU data centres. Formerly known as Orbital Materials; completed a rebrand to Orbital Industries and raised a $50 million Series B in May 2026.

Ori Biotech

ScaleupBiotech & Life SciencesDeep TechBritish

Biomanufacturing technology company offering a full-stack closed and automated platform (the IRO system) to standardise and scale cell and gene therapy manufacturing. The IRO platform received FDA Advanced Manufacturing Technology designation in September 2025, one of the first technologies to do so.

Oriole Networks

ScaleupAIClimateBritish

UCL spin-out using photonics to connect AI chips with light, enabling large language models to be trained up to 100x faster while consuming a fraction of the power of conventional data-centre interconnects.

Orrick

Professional ServicesLegalForeign

Orrick, Herrington & Sutcliffe LLP is a global law firm tracing its roots to 1863 in San Francisco, with a focus on technology and innovation, energy and infrastructure, finance, and life sciences. The firm serves leading companies and investors across more than 25 offices worldwide, including a London office.

Orthogonal Peptides

StartupBiotech & Life SciencesDeep TechBritish

Peptide therapeutics spinout from Imperial College London developing a novel solid-phase peptide synthesis method that produces multiple fragments per bead, enabling manufacture of complex cyclic and conjugate peptides while reducing synthesis waste by approximately 50%.

Osborne Clarke

Professional ServicesLegalBritish

Osborne Clarke is an international law firm with origins in Bristol in 1748, now headquartered in London with over 26 offices across Europe, Asia, and North America. The firm serves clients in sectors including technology, media and telecoms, energy, life sciences, financial services, and the built environment, with more than 1,600 lawyers across its global network.

Oura

ScaleupBiotech & Life SciencesDeep TechForeign

Enhance your health journey with Oura. The Oura Ring provides round-the-clock insights into sleep, fitness, and stress for wellness. Now HSA/FSA eligible.

OutSystems

CorporateSaaSAIForeign

OutSystems combines a low-code foundation with AI-driven software development to deliver enterprise apps and custom agents with full SDLC governance.

OutThink

ScaleupCybersecurityAIBritish

AI human risk management platform that predicts and prevents human-initiated security incidents.

Outpost Bio

StartupBiotech & Life SciencesDeep TechForeign

Outpost is building the AI layer for human microbiology. 

Our lab-in-the-loop models can decode the microbiome and transform modern medicine.

Outward VC

VCFinanceProptechBritish

Outward VC is a London-based early-stage venture capital firm investing in founders solving important problems at the intersection of financial services and society. The firm backs companies across fintech and adjacent sectors including insurtech, proptech, healthtech, edtech, and legaltech, with a people-first investment philosophy.

Overmind

StartupAI SafetyCybersecurityBritish

Supervision and security layer for autonomous AI agents, using pattern-of-life analysis and reinforcement learning to monitor, flag, and improve agentic AI behaviour in real time, targeting regulated sectors such as legal, healthcare, and fintech.

Overwolf

ScaleupGamingMediaForeign

Overwolf is the all-in-one platform that lets creators build, share and monetize in-game apps and mods. We help developers supercharge games with creator-made content and make a living doing what they love.

Oviva

ScaleupBiotech & Life SciencesConsumerForeign

Digital health platform delivering app-based treatment for diabetes, obesity, and diet-related conditions, with programmes commissioned by the NHS and private insurers across the UK and Europe.

Ovo Energy

CorporateClimateBritish

Learn about our tree Planting Promise and switch to OVO Energy today for fair, competitive energy prices.

Ovo Labs

StartupBiotech & Life SciencesDeep TechForeign

Fertility technology company developing treatments to improve IVF success rates, focused on egg quality and chromosomal errors in women over 35.

OxAngels

VCOtherBritish

OxAngels is an angel investment group comprising individuals with a connection to the University of Oxford who are passionate about supporting early-stage and start-up companies to create social and economic value through innovation and entrepreneurship.