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Specialty Lines insurers
- Global and national commercial carriers 15
- Regional carriers 20
- Personal-lines carriers that also insure businesses 9
- Specialty and E&S insurers 31
- Workers' comp specialists and state funds 7
- Medical and professional liability specialists 3
- Niche and affinity insurers 9
- Small business specialists 12
- Cyber specialists 3
- Program carriers and fronting insurers 6
- Reinsurer-owned commercial insurers 5
| # | Insurer | Type | Commercial premiums (2025) | AM Best |
|---|---|---|---|---|
| 2 | ChubbGlobal insurer and the No. 1 U.S. writer of business liability coverage. A++ rated, with Westchester for E&S and online quotes for small firms. | Global and national commercial carriers | $23.25 billion | A++ (Superior) |
| 3 | Liberty MutualBoston-based mutual and No. 3 U.S. business insurer. Leading surety writer, sells small business coverage through independent agents and E&S via Ironshore. | Global and national commercial carriers | $19.93 billion | A (Excellent) |
| 4 | Berkshire HathawayNo. 4 U.S. business insurer through a family of separately run units: BHSI, MedPro, GUARD, biBERK, USLI, RSUI and BHHC. Major units rated A++ by AM Best. | Global and national commercial carriers | $18.64 billion | A++ (Superior) |
| 7 | AIGGlobal commercial insurer for middle-market, large and multinational companies, led in the U.S. by National Union and Lexington, the E&S arm. Broker-sold. | Global and national commercial carriers | $14.45 billion | A (Excellent) |
| 8 | CNAChicago commercial insurer controlled by Loews, sold through agents and brokers. Strong in professional liability, healthcare, surety and specialty lines. | Global and national commercial carriers | $13.47 billion | A+ (Superior) |
| 10 | W. R. BerkleyGreenwich, Conn., insurer running about 60 specialized units in E&S, specialty, regional and workers' comp lines, sold through agents, brokers and wholesalers. | Specialty and E&S insurers | $10.24 billion | A+ (Superior) |
| 11 | Tokio MarineJapan's Tokio Marine owns Philadelphia Insurance, Tokio Marine HCC and Safety National: niche package, specialty lines and excess workers' comp. | Global and national commercial carriers | $9.53 billion | A++ (Superior) |
| 13 | Fairfax FinancialToronto-based Fairfax owns Crum & Forster, Allied World, Zenith and Hudson: specialty, excess and surplus lines and workers' comp sold through brokers. | Specialty and E&S insurers | $9.09 billion | A+ (Superior) |
| 14 | NationwideColumbus mutual writing small business, middle market, agribusiness, E&S and program business through independent agents; No. 2 in U.S. farmowners. | Global and national commercial carriers | $8.08 billion | A (Excellent) |
| 15 | MarkelVirginia specialty insurer writing E&S, professional liability, programs, surety and niche small business packages through wholesalers, agents and MGAs. | Specialty and E&S insurers | $7.73 billion | A (Excellent) |
| 18 | Starr Insurance CompaniesPrivately held global specialty insurer based in New York; the No. 1 U.S. writer of commercial fire and aircraft insurance and No. 2 in ocean marine. | Specialty and E&S insurers | $7.29 billion | A (Excellent) |
| 19 | Great American Insurance GroupCincinnati specialty insurer owned by American Financial Group (NYSE: AFG), running 30-plus niche units in comp, trucking, construction, crime and marine. | Specialty and E&S insurers | $7.11 billion | A+ (Superior) |
| 21 | Allianz CommercialAllianz's commercial arm (formerly AGCS, absorbing Fireman's Fund); large corporate property, casualty, marine, aviation and specialty cover through brokers. | Global and national commercial carriers | $6.61 billion | A+ (Superior) |
| 23 | AmTrust FinancialNew York-based, privately held insurer; the No. 3 U.S. workers' comp writer, also selling BOPs, packages, E&S and MGA programs through agents. | Workers' comp specialists and state funds | $6.25 billion | A- (Excellent) |
| 25 | Arch InsuranceU.S. arm of Bermuda-based Arch Capital; specialty, E&S and (since buying Allianz's book in 2024) middle market P&C through brokers, MGAs and programs. | Specialty and E&S insurers | $5.61 billion | A+ (Superior) |
| 28 | SompoBermuda-based commercial arm of Japan's Sompo Holdings (formerly Endurance): casualty, property, professional lines, surety and crop through brokers. | Specialty and E&S insurers | $4.66 billion | A+ (Superior) |
| 29 | The HanoverWorcester, Mass., agency carrier (est. 1852) writing small and midsize business packages, comp and auto, plus specialty lines, in 44 states and D.C. | Regional carriers | $4.21 billion | A (Excellent) |
| 31 | Munich ReThe German reinsurer's U.S. arm: Munich Re Specialty's E&S, public entity, surety and program business, plus HSB equipment breakdown and NEXT. | Reinsurer-owned commercial insurers | $3.94 billion | A+ (Superior) |
| 32 | MSIG USAU.S. commercial arm of Japan's MS&AD: property, casualty, marine and financial lines for mid-size and multinational firms, plus MS Transverse fronting. | Global and national commercial carriers | $3.42 billion | A+ (Superior) |
| 34 | AXIS CapitalBermuda-based specialty insurer selling E&S casualty and property, professional, management, cyber and construction lines to mid-size and large U.S. firms. | Specialty and E&S insurers | $3.23 billion | A (Excellent) |
| 39 | WestfieldOhio regional founded in 1848, selling commercial, farm and surety coverage through independent agents, plus E&S and Lloyd's capacity via Westfield Specialty. | Regional carriers | $2.48 billion | A (Excellent) |
| 40 | Core SpecialtyCincinnati specialty insurer built from StarStone U.S. in 2020; writes E&S and admitted casualty, property, Lancer auto, comp and bonds via brokers. | Specialty and E&S insurers | $2.47 billion | A (Excellent) |
| 42 | Argo Group and Farm Family (Clearbrook)Brookfield's U.S. P&C arm: Argo specialty casualty, E&S, garage and Rockwood comp through brokers, plus Farm Family farm and small business cover. | Specialty and E&S insurers | $2.21 billion | A- (Excellent) for Argo companies; A (Excellent) for Farm Family Insurance Group |
| 45 | QBE North AmericaU.S. arm of Australia's QBE, writing specialty casualty, financial lines, construction, large-account property, programs, A&H and crop via brokers and agents. | Specialty and E&S insurers | $2.05 billion | A (Excellent) |
| 46 | Intact Insurance Specialty SolutionsU.S. specialty arm of Canada's Intact Financial (formerly OneBeacon), writing surety, marine, A&H, tech, entertainment and management liability via brokers. | Specialty and E&S insurers | $1.94 billion | A+ (Superior) |
| 47 | BeazleyLloyd's specialty insurer known for cyber, D&O and E&S property, acquired by Zurich on Oct. 1, 2026; sells through brokers on admitted, E&S and Lloyd's paper. | Specialty and E&S insurers | $1.94 billion | A (Excellent) |
| 48 | Kinsale InsuranceRichmond, Va., E&S-only insurer founded in 2009, writing hard-to-place casualty, property and professional risks for small and midsize firms via wholesalers. | Specialty and E&S insurers | $1.93 billion | A (Excellent) |
| 50 | RLIPeoria, Illinois specialty insurer writing E&S and niche admitted casualty, property, trucking and surety through brokers and agents; rated A++ by AM Best. | Specialty and E&S insurers | $1.83 billion | A++ (Superior) |
| 53 | AccelerantA risk exchange whose insurers issue policies for 300-plus specialty MGAs insuring small and mid-sized businesses; a Thoma Bravo buyout is pending. | Program carriers and fronting insurers | $1.60 billion | A- (Excellent), under review with developing implications since August 2026 |
| 55 | Ascot GroupBermuda specialty insurer majority-owned by CPP Investments; its U.S. arm writes E&S and excess casualty, professional lines, surety, marine and comp. | Specialty and E&S insurers | $1.58 billion | A (Excellent) |
| 56 | The Doctors CompanyPhysician-owned med mal insurer based in Napa, California, covering doctors, dentists, clinicians and hospitals. It bought ProAssurance in June 2026. | Medical and professional liability specialists | $1.55 billion | A (Excellent) |
| 57 | IAT Insurance GroupPrivate Raleigh specialty carrier writing trucking and moving insurance, inland marine, E&S casualty and property, surety and management liability via agents. | Specialty and E&S insurers | $1.54 billion | A- (Excellent) |
| 58 | Coaction SpecialtyNew Jersey specialty insurer (formerly ProSight) owned by TowerBrook and Further Global: E&S casualty and property, marine, energy, entertainment and D&O. | Specialty and E&S insurers | $1.51 billion | A- (Excellent) |
| 60 | Skyward SpecialtyHouston-based specialty insurer writing E&S, surety, professional lines, energy, programs, captives and stop-loss; bought Lloyd's platform Apollo in 2026. | Specialty and E&S insurers | $1.41 billion | A (Excellent) |
| 62 | TrisuraToronto-listed specialty insurer whose Oklahoma City-based U.S. arm issues policies for MGA programs and is building a U.S. surety business. | Program carriers and fronting insurers | $1.34 billion | A- (Excellent) |
| 63 | FortegraJacksonville specialty insurer writing E&S and admitted programs through MGAs plus warranty and credit protection; owned by Korea's DB Insurance since May 2026. | Specialty and E&S insurers | $1.33 billion | A (Excellent) |
| 66 | TruStage (CUMIS)The credit union movement's own insurer, formerly CUNA Mutual Group; CUMIS writes bonds, D&O, cyber and property for credit unions plus specialty programs. | Niche and affinity insurers | $1.20 billion | A (Excellent) |
| 67 | UFG InsuranceCedar Rapids, Iowa, commercial insurer founded in 1946, selling packages, auto, comp and surety through about 850 independent agencies; Nasdaq: UFCS. | Regional carriers | $1.18 billion | A- (Excellent) |
| 68 | Aspen InsuranceBermuda specialty insurer and reinsurer owned by Apollo funds from 2019 and by Sompo since February 2026; known for excess casualty, professional lines and E&S. | Specialty and E&S insurers | $1.18 billion | A+ (Superior) |
| 71 | James RiverNasdaq-listed E&S casualty writer for small and mid-size accounts, sold only through wholesalers, plus Falls Lake admitted comp; rated A-, negative outlook. | Specialty and E&S insurers | $1.13 billion | A- (Excellent), negative outlook |
| 72 | Western NationalMinnesota mutual selling commercial package, auto, comp, niche programs and surety through independent agents in the Upper Midwest, Northwest and Alaska. | Regional carriers | $1.09 billion | A+ (Superior) |
| 73 | HDI GlobalU.S. arm of Germany's Talanx/HDI: broker-placed property, casualty and specialty for mid-size and large companies, rated A+ by AM Best. | Reinsurer-owned commercial insurers | $1.07 billion | A+ (Superior) |
| 81 | ProAssuranceBirmingham-based medical malpractice, med-tech products and workers' comp insurer, owned by The Doctors Company since June 2026 after a $1.3 billion takeover. | Medical and professional liability specialists | $927.0 million | A (Excellent) |
| 84 | PalomarLa Jolla specialty insurer known for earthquake and DIC property, now growing in contractor casualty, inland marine, surety, crop and fronting. | Specialty and E&S insurers | $890.2 million | A (Excellent), stable outlook (Palomar Specialty and Palomar Excess and Surplus; First Indemnity of America A-, positive) |
| 85 | Sutton NationalA-rated program carrier that issues admitted and surplus lines policies for program administrators and reinsurers; you reach it only through a program. | Program carriers and fronting insurers | $877.4 million | A- (Excellent), stable outlook |
| 86 | Obsidian InsuranceGenstar-backed hybrid fronting carrier that issues policies for MGA and program administrator programs; Protective Life agreed to buy it in April 2026. | Program carriers and fronting insurers | $866.6 million | A- (Excellent), under review with positive implications |
| 87 | Vantage RiskBermuda specialty (re)insurer founded in 2020 that writes U.S. excess casualty, construction, healthcare and large property; owned by Howard Hughes since 2026. | Specialty and E&S insurers | $822.5 million | A- (Excellent), positive outlook |
| 95 | MagMutualAtlanta-based physician-owned mutual that insures doctors, medical groups and hospitals for malpractice; online quoting for physicians, rated A (Excellent). | Medical and professional liability specialists | $677.2 million | A (Excellent) |
| — | Allied WorldFairfax-controlled Bermuda specialty insurer writing excess casualty, D&O, healthcare, environmental and property for midsize and large U.S. accounts. | Specialty and E&S insurers | — | A+ (Superior) |
| — | Berkshire Hathaway Specialty InsuranceBerkshire Hathaway's Boston-based specialty arm, launched in 2013: property, casualty, D&O, E&O, healthcare liability, surety and marine through brokers. | Specialty and E&S insurers | — | A++ (Superior) |
| — | Crum & ForsterFairfax's Morristown specialty carrier: admitted and E&S casualty, construction, property, surety and accident and health, sold through agents and wholesalers. | Specialty and E&S insurers | — | A+ (Superior) |
| — | EmbrokerDigital insurance broker and MGA for startups, tech companies and law firms. Its own programs are written on Everest National and Everspan paper. | Small business specialists | — | — |
| — | Lloyd'sLondon insurance market of about 100 syndicates, rated A+ by AM Best. U.S. firms reach it as surplus lines cover through brokers, wholesalers and coverholders. | Specialty and E&S insurers | — | A+ (Superior) |
| — | Philadelphia Insurance CompaniesTokio Marine's PHLY writes package, auto and management liability for 120-plus niches, from nonprofits and HOAs to gyms, camps and special events. | Niche and affinity insurers | — | A++ (Superior) |
| — | VouchInsurance broker for startups, tech, life sciences and financial firms. Sold its Corix MGA and Vouch Insurance Company to Hiscox under a 2025 deal. | Small business specialists | — | — |
Ranked by 2025 U.S. commercial lines direct premiums written: NAIC 2025 market share data for 17 commercial lines (states and U.S. territories), summed by insurance group. A group's premium in a line where it is outside NAIC's top 125 is not counted. Seven groups are left out because a business cannot buy from them or their premium in these lines is mostly consumer coverage: USAA, CSAA, the Ohio Bureau of Workers' Compensation, Florida's Citizens, the Texas FAIR Plan and windstorm pool, Assurant and Generali. Brands without a rank are well-known companies inside these groups or outside the top 100.