Timothée Lacroix
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Timothée Lacroix is a French artificial intelligence researcher and engineer who is a co-founder and the chief technology officer of Mistral AI, the Paris-based developer of open-weight large language models.[1][2] Before starting the company in 2023, he spent several years at Facebook AI Research (FAIR), later Meta AI, where he worked on machine learning for knowledge bases and was a co-author of the original LLaMA paper.[2][3][4] He founded Mistral AI together with Arthur Mensch and Guillaume Lample, two researchers he had worked alongside in Paris.[1][5]
Lacroix's work sits on the engineering side of large-scale machine learning, from his doctoral research on tensor methods for relational data to the systems and training pipelines behind frontier language models.[4][6] At Mistral AI he is responsible for the company's technical direction and its model research and infrastructure, complementing co-founder Guillaume Lample, who serves as chief science officer, and chief executive Arthur Mensch.[1][2] The three founders built Mistral into one of Europe's most prominent AI companies within a few years of its launch, reaching a valuation of about 11.7 billion euros by late 2025.[7][8]
Lacroix is a graduate of the École Normale Supérieure (ENS) in Paris.[5][9] He went on to complete a master's degree associated with the Paris region universities and then a PhD focused on machine learning, carried out in connection with the École des Ponts ParisTech (ENPC) while he was working at Facebook AI Research.[9][6] Unlike his two co-founders, Arthur Mensch and Guillaume Lample, who are both alumni of the École Polytechnique (class of 2011), Lacroix came through ENS rather than Polytechnique; the founders' paths converged through the Paris machine learning community and their shared time at Meta rather than a single school.[5][9]
His doctoral research centered on knowledge base completion, the problem of predicting missing facts in large relational datasets. As first author he published "Canonical Tensor Decomposition for Knowledge Base Completion" at the International Conference on Machine Learning (ICML) in 2018, work that reframed knowledge base completion as low-rank tensor decomposition and introduced a nuclear-norm-based regularizer that improved accuracy on standard benchmarks.[6][10] He later extended the approach to time-evolving data in "Tensor Decompositions for Temporal Knowledge Base Completion," presented at the International Conference on Learning Representations (ICLR) in 2020.[10][11]
Lacroix joined Facebook AI Research in Paris, first as a PhD student and subsequently as a research engineer, and remained there until co-founding Mistral.[5][9] His earliest work at the company continued his thesis line on embedding methods and tensor factorization for knowledge bases, an area where representations of entities and relations are learned so that plausible facts score higher than implausible ones.[6][10]
Over time his focus shifted toward large language models. He is listed as a co-author of "LLaMA: Open and Efficient Foundation Language Models," the February 2023 paper that introduced Meta's first LLaMA family of models and was led by Guillaume Lample, with Hugo Touvron as lead author.[3] LLaMA showed that comparatively small models trained on more tokens could match or exceed much larger systems, and its release, including the leak and subsequent open distribution of the weights, helped seed a wave of open-source language model development.[3] French press covering Mistral has described Lacroix as a former Meta researcher and Lample as one of LLaMA's creators, the engineering and research background the pair carried into their own company.[5]
Lacroix co-founded Mistral AI on 28 April 2023 with Arthur Mensch, who had spent about three years at Google DeepMind, and Guillaume Lample, his former FAIR colleague.[1][5] The company positioned itself as a European builder of open and efficient foundation models, an explicit contrast to the more closed approach of larger United States labs.[7]
Mistral attracted capital unusually quickly for a company at its stage. The table below summarizes its main early funding milestones.
| Round | Date | Amount | Notes |
|---|---|---|---|
| Seed / Series A | June 2023 | about 105 million euros | Led by Lightspeed Venture Partners; valuation around 240 million euros[7][12] |
| Series B | December 2023 | about 385 million euros | Investors including Andreessen Horowitz; valuation near 2 billion dollars[7][12] |
| Series C | September 2025 | about 1.7 billion euros | Led by ASML, with Nvidia among backers; valuation about 11.7 billion euros[8][13] |
The 2025 round, which valued Mistral at roughly 11.7 billion euros (about 14 billion dollars), was led by the Dutch semiconductor-equipment maker ASML and made the three founders among the first home-grown AI billionaires in France on paper.[8][13] Mistral's products include its open-weight model families and Le Chat, a conversational assistant marketed as a European alternative to other mainstream chatbots.[7][8]
As CTO, Lacroix leads Mistral's technical organization, overseeing model research, training, and the engineering of the systems that serve the company's models.[1][2] Public profiles and the company's own about page list him simply as "Co-founder and CTO," alongside Mensch as CEO and Lample as chief science officer.[1][2] In interviews and talks he has emphasized efficiency in model training and inference, the discipline of getting strong results from constrained compute budgets, which has been central to Mistral's strategy of competing with far larger rivals.[14]
His Google Scholar profile, which lists affiliations with Facebook AI Research and the École des Ponts, records his research output on knowledge base completion and language modeling, including the LLaMA paper among his most cited work.[4]