Nuclear startups defy climate tech slump with record funding for 2025

Global VC funding for climate tech is on course for its worst finish – $29 billion – since 2017, according to Dealroom data.

However, nuclear fusion and fission startups are bucking the trend. Globally, they’ve already raised $3.7 billion in 2025, overtaking 2021, the previous record year.

In Europe, nuclear startups have raised $475m, just shy of 2022’s $541m (mainly thanks to a single, €300m raise by Paris-based nuclear fission startup Newcleo).

Europe's fusion boom

For Europe's fusion energy startups, 2025 was a breakout year – with $340m in the coffers already – far surpassing the previous record of $217m in 2024.

One fusion energy startup, Munich-based Proxima Fusion, closed a €130m Series A round in June in Europe's largest single private investment in the technology, which smashes atoms to generate clean power.

Proxima’s co-founder and CEO, Francesco Sciortino, said the funding gives it a “powerful European foundation” to lead the global race to fusion. The company’s backers include Balderton Capital, Cherry Ventures, and Plural.

Another emerging fusion energy player is Marvel Fusion, which secured €113mn in a Series B funding round in March led by investors including EQT and Siemens Energy. In Sweden, there's Novatron, which secured €10mn earlier this year to build a unique type of fusion reactor it calls a “mirror machine.”

Europe rethinks nuclear

While some startups are looking to fuse atoms together, others are looking to rip them apart – as part of a European nuclear fission renaissance.

These companies, however, are focussing their efforts on smaller, modular reactors instead of the mega plants of times past.

Finland's Steady Energy has secured Europe's largest nuclear fission funding round so far this year – a €32m investment led by 92 Capital, a Danish VC firm dedicated to nuclear energy.

Steady Energy was founded in 2023 by Tommi Nyman, Hannes Haapalahti, and Petteri Tenhunen as a spin-off from VTT Technical Research Centre of Finland. It aims to build the world's first small modular reactor (SMR), in the capital of Helsinki.

Meanwhile, Dutch startup Thorizon, head by CEO Kiki Lauwers, secured €16m for its reactor that reuses nuclear waste, and French startup Stellaria bagged €23m for to advance its chloride molten salt reactor, aiming for a working prototype by 2029.

Combined, Europe’s nuclear startups are carving out a rare bright spot in climate tech – and positioning the continent as a serious contender in the global race for clean energy.

Pictured from left: Kiki Lawuers, CEO of Thorizon, Francesco Sciortino, CEO and co-founder of Proxima Fusion, Hannes Haapalahti, CTO & co-founder at Steady Energy, and Marvel Fusion's COO Heike Freund.