Thirdbase Capital Research
Investment Thesis
Thirdbase Capital is a New York-based private markets investment firm founded in 2019 by Abhinav Gupta. The firm describes itself as "a global private markets investment firm focused on high-conviction investments in transformative technology companies." In practice this means concentrated, opportunistic checks into a short list of category-defining AI, infrastructure, fintech, and deep-tech companies rather than a high-volume seed program. The firm also operates under the name 535West (a reference to its 535 W 23rd Street, New York office), which appears to be used interchangeably with the Thirdbase Capital brand across secondary databases and the firm's own site copy.
Stage Focus
Public trackers describe Thirdbase as targeting Series A and Series B rounds, but its actual disclosed portfolio skews much later: SpaceX, OpenAI, Anthropic, Databricks, Groq, and Kalshi are all growth-stage or pre-IPO companies by the time Thirdbase's involvement is typically recorded. This pattern is consistent with a fund that uses primary Series A/B commitments as an entry thesis but also participates opportunistically in later rounds and secondaries of already-breakout companies, likely via SPVs alongside larger lead investors.
Check Size
Typical check size is reported at $500K to $20M, with a stated sweet spot around $10M. This range is small relative to the size of the rounds its most visible portfolio companies raise (e.g., Kalshi's ~$1B Series F, Databricks' multi-billion-dollar rounds), reinforcing that Thirdbase is a participant rather than an anchor investor in its highest-profile positions.
Lead Tendency
Thirdbase does not appear to lead its marquee investments. Where syndicate composition is visible (e.g., Kalshi's Series F was led by Coatue with Sequoia, a16z, IVP, Paradigm, Morgan Stanley, and ARK Invest), Thirdbase is one of many smaller participants. Lead tendency is best characterized as "follows."
Recent Activity
The most recent identifiable investment is Kalshi, tied to Kalshi's ~$1B Series F round that closed around May 2026 at a $22B valuation. Beyond that specific event, third-party portfolio trackers (PitchBook, Crunchbase, Tracxn) list Thirdbase against a cluster of 2024-2026 AI and deep-tech names, but do not consistently expose per-round dates or press confirmation of Thirdbase's specific participation, so this document does not assert exact dates for the rest of the portfolio.
Portfolio Highlights
The firm's own homepage names sixteen portfolio companies, spanning frontier AI labs (Anthropic, OpenAI, Reflection AI), AI infrastructure and compute (Databricks, Groq, Crusoe, Decart), fintech (Kalshi, Aven), healthcare AI (Abridge), biotech (Colossal Biosciences, Loyal), energy and materials (Aalo Atomics, Redwood Materials), robotics (Gecko Robotics), and aerospace (SpaceX). Two portfolio companies (SpaceX, Rubrik per third-party trackers) have reached public markets, and the portfolio includes multiple companies at unicorn-plus valuations (Anthropic, OpenAI, Databricks, Kalshi).
Team
- Abhinav Gupta, Founder & Managing Partner - Holds a finance and entrepreneurship degree from Boston University. Prior to investing, he founded and scaled two direct-to-consumer brands (The Essential Goods, White Spindle) and has been described as CEO of Moving Capital. He is the sole named managing partner across public trackers.
- Nitya Singh, Investor - Based in India, works across Thirdbase Capital and 535West on sourcing and diligence. Prior experience includes KPMG India and roles in entrepreneurship-focused organizations (BEAM). LinkedIn: https://in.linkedin.com/in/nityasingh19
Decision Process
With only two people publicly associated with the firm and one named managing partner, Thirdbase reads as a solo-GP-style operation rather than a multi-partner investment committee.
Founder Preferences
Public materials do not articulate an explicit founder profile. Given the portfolio's composition, the firm gravitates toward category-leading teams in AI, deep tech, fintech, and energy that are already validated by top-tier lead investors, rather than backing unproven first-time founders pre-signal.
Geographic Focus
Thirdbase is headquartered in New York (535 W 23rd Street) and its visible portfolio is overwhelmingly US-based, with no clear international investment pattern surfaced in available sources.