Marsh McLennan
Global professional services firm
Marsh & McLennan Companies, Inc., trading as Marsh McLennan and Marsh, is an American professional services firm headquartered in New York City, with businesses in insurance brokerage, risk management, reinsurance services, talent management, investment advisory, and management consulting. Its four main operating companies are Marsh (54% of 2025 revenues), which offers risk management, insurance broking, insurance program management, risk consulting, analytical modeling, and alternative risk financing services; Marsh Re (formerly Guy Carpenter; 10% of 2025 revenues), a reinsurance intermediary and advisor; Mercer (23% of 2025 revenues), which provides consulting to employers for health insurance, retirement plans, and pension plans; and Oliver Wyman (13% of 2025 revenues), including Lippincott and NERA Economic Consulting, which provides consulting services. In 2024, risk and insurance services contributed a total of 63% of revenues and 71% of operating profit, while consulting contributed 37% of revenues and 29% of operating profit.
It is the largest insurance broker worldwide.
The company is ranked 175th on the Fortune 500 and 267th on the Forbes Global 2000.
History
1900–1999
Burroughs, Marsh & McLennan was formed by Henry W. Marsh and Donald R. McLennan in Chicago in 1905 by the merger of their two businesses. Marsh founded his business in 1871 after many insurers went out of business after the Great Chicago Fire. The combined company was renamed Marsh & McLennan in 1906.
Guy Carpenter was acquired in 1923, a year after it was founded by Guy Carpenter.
In 1959, Marsh acquired Mercer, a human resources consulting firm.
This brief starts where responsible research should: with the source description of “Marsh McLennan” as global professional services firm. Everything that follows is an evidence route, not borrowed authority.
Why this record matters
The subject matters to the general reference register because the source frames it as global professional services firm. Its deeper value depends on whether names, dates, institutions and citations support that framing.
Vocabulary and entity names are the principal evidence signals here, because they determine the precision of every later search. The source revision retrieved here is dated Sep 18, 2026. The linked authority identifier is Q1786345. VIAF identifies the subject as 132480750. The Library of Congress control number is no92005167. 2 of 4 selected statements include explicit references; 0 carry qualifiers and 0 use preferred rank. The first chronological checks are 2025, 2024, 2000 and 1900.
The absence of detail may reflect summary conventions rather than a lack of surviving documentation. The source lead contains qualifying language; that uncertainty should survive quotation, summary and reuse. Authority statements aid reconciliation but still require their own references, qualifiers and ranks to be checked.
How to read it
Use the entry as an orientation point, then follow its citations and revision history. Names, dates and institutional relationships should be checked against the original record.
- Subject orientation
- Search vocabulary
- Locating named sources
The closest primary source, responsible institution and strongest cited specialist reference.
Three-step research path
- Establish the record: confirm the title “Marsh McLennan”, its source revision and the description used here.
- Expand the search: follow Marsh McLennan primary sources, Marsh McLennan archive and Marsh research across catalogues and specialist indexes.
- Test the account: compare the strongest cited source with the responsible institution’s current record and note any disagreement.
Questions for further research
- Which source most directly establishes the central claim about “Marsh McLennan”?
- Which cited source is closest to the event, object or claim?
- What terminology or title could unlock a more precise catalogue search?
Search terms from this dossier
This entry incorporates text from “Marsh McLennan” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.