Startup · United States

Deep Fission

HQ BerkeleyFounded 202351-200 employeesFISN

Deep Fission is an advanced nuclear energy deployment company developing small modular pressurized water reactors designed to operate one mile underground. Advanced nuclear for the AI era.

StartupDevelopmentSmall modular reactors

Funding4 rounds · $154M

Equity raised: $154M
Latest: $40.0MIPO · Jun 17, 2026

Cumulative raised$154M

Aug 22, 2024Jun 17, 2026

Funding rounds
Announced	Stage	Amount	Valuation	Lead investors	Other investors	Confidence
Jun 17, 2026	IPO	$40.0M	—	—	—	Confirmed
Feb 10, 2026	Undisclosed	$80.0M	—	—	—	Confirmed
Sep 8, 2025	SPAC	$30.0M	—	Montrose Capital Partners	8VC	Confirmed
Aug 22, 2024	Pre-Seed	$4.0M	—	8VC	—	Confirmed

IPO
Confirmed
$40.0M
Jun 17, 2026
Undisclosed
Confirmed
$80.0M
Feb 10, 2026
SPAC
Led by Montrose Capital Partners
With 8VC
Confirmed
$30.0M
Sep 8, 2025
Pre-Seed
Led by 8VC
Confirmed
$4.0M
Aug 22, 2024

Raised counts equity rounds; debt, secondary sales and grants are totaled separately. Amounts in other currencies are converted at the announcement month's average rate. A ~ marks an estimated or converted amount.

Systems1

Gravity Nuclear Reactor

An underground pressurized-water nuclear reactor design under development.

Maturity not rated

Newest unveiled first. Open a system for its milestone timeline, components and sources.

Capabilities1

Capabilities
Technology	Role	Maturity	TRL	Notes	Confidence
Small modular reactors	Developer	Development	—	—	Reported

Small modular reactors
Developer
DevelopmentReported

Maturity and TRL describe this organization's work; the field-wide maturity is on each technology's page.

People2

All 2 people →

Elizabeth Muller
Founder
Liz Muller
CEO

Sources16

Show all 16 sources and supporting evidence

Profile4

1
DatabaseDeep Fission - PitchBook company profile
PitchBook · Supports Organization · employee range, Organization · founded year, Organization · linkedin url, Organization · x url
“employee_range: 51-200 (profile: 62)”
2
DatabaseSixth-Domain public startups directory
Sixth-Domain · Supports Organization · country, Organization · kind
“{"country": "USA", "hq_iso2": "US", "id": "c13e0f5d-c155-40c7-9fa1-1c062f9eb0a7"}”
3
DatabaseDeep Fission - LinkedIn company profile
LinkedIn · Supports Organization · employee range, Organization · founded year, Organization · hq city, Organization · linkedin url
“employee_range: 51-200 (profile: 51-200 employees)”
4
Government recordSEC company tickers and exchanges
U.S. Securities and Exchange Commission · Supports Organization · ownership
“[1918102,"DEEP FISSION, INC.","FISN","Nasdaq"]”

Systems1

5
CompanyGravity Reactor™ | Small modular PWR a mile underground
Deep Fission · Supports System
“Deep Fission’s Gravity Nuclear Reactor technology taps into one of nature’s most reliable forces intended to support safety functions, reduce surface infrastructure, and enable more repeatable deployment.”

Technologies1

6
CompanyAdvanced nuclear energy deployment :: Deep Fission, Inc. (FISN)
Deep Fission · Supports Organization · description, Organization · name, Organization · website, Organization technology
“Deep Fission is an advanced nuclear energy deployment company developing small modular pressurized water reactors designed to operate one mile underground. Advanced nuclear for the AI era.”

Funding8

7
CompanyAdvanced Nuclear Company Deep Fission Announces Pricing of Public Offering of Common Stock
Deep Fission (Business Wire) · Jun 18, 2026 · Supports Funding round · amount
“today announced the pricing of its public offering of 2,500,000 shares of its common stock at a public offering price of $16.00 per share, for total gross proceeds of $40 million.”
8
NewsNuclear tech developer Deep Fission prices IPO at $16, the low end of the downwardly revised range
Renaissance Capital · Jun 18, 2026 · Supports Funding round
“raised $40 million by offering 2.5 million shares at $16, the low end of the $16 to $18 range.”
9
Regulatory filingForm D: DEEP FISSION, INC.
U.S. Securities and Exchange Commission · Feb 18, 2026 · Supports Funding round · amount
“Issuer: DEEP FISSION, INC.; Date of First Sale: 2026-02-05; Total Amount Sold: 79999995”
10
CompanyDeep Fission Advanced Nuclear Raises $80 Million in Financing to Accelerate Commercialization
Deep Fission (Business Wire) · Feb 10, 2026 · Supports Funding round · amount
“announced today it has raised $80 million in new financing”
11
Regulatory filingForm D: DEEP FISSION, INC.
U.S. Securities and Exchange Commission · Sep 23, 2025 · Supports Funding round · amount
“<totalAmountSold>30000000</totalAmountSold>”
12
NewsDeep Fission goes public with $30m private placement offering
Power Technology · Sep 9, 2025 · Supports Funding round
“has gone public through a reverse merger transaction with Surfside Acquisition and raised $30m through a private placement offering.”
13
NewsNuclear startup Deep Fission goes public in a curious SPAC
TechCrunch · Sep 8, 2025 · Supports Funding round · amount
“announced Monday that it has gone public in a reverse merger, netting the company $30 million.”
14
CompanyBreakthrough Nuclear Startup, Deep Fission, Emerges from Stealth Mode with $4M in Backing
Deep Fission (Business Wire) · Aug 22, 2024 · Supports Funding round · amount
“today announced its emergence from stealth mode and a $4 million pre-seed round, led by 8VC.”

People2

15
NewsDeep Fission, Inc. - Wikipedia
en.wikipedia.org · Supports Role
“Deep Fission was founded in 2023 by Elizabeth Muller and Richard A.”
16
CompanyDeep Fission, Inc.
Deep Fission · Supports Role
“Aug 3, 2026 8:30 am EDT Deep Fission CEO Liz Muller to Present at Canaccord Genuity’s 46th Annual Growth Conference Read More”

Each fact on this page is attached to the sources that support it. Archived copies are linked when we keep one.