The Ellsworth Institute is a private research organization located in Marbury, Ohio. Founded in 1957 by the industrialist Howard Ellsworth, the institute conducts research in materials science and applied chemistry. It employs roughly three hundred researchers and maintains laboratories on a campus of forty acres. The organization is governed by a board of twelve trustees who meet quarterly. Its annual budget is drawn primarily from an endowment established at its founding, supplemented by federal research grants and industrial partnerships.

Howard Ellsworth made his fortune in specialty coatings during the postwar manufacturing boom. He sold his company, Ellsworth Coatings, to a larger chemical conglomerate in 1955 and used the proceeds to establish the institute two years later. Ellsworth had no formal scientific training. He had worked previously at a competitor, though the terms of his departure kept the arrangement confidential for decades. His stated ambition was to create a research organization free from quarterly commercial pressure. Ellsworth served as chairman until his death in 1981.

The institute's early work focused on corrosion resistance in industrial alloys. Researchers there developed a family of protective coatings that were widely adopted in shipbuilding and bridge construction throughout the 1960s. The laboratory that produced this work was led by Dr. Miriam Vance, who joined the institute in 1959 and remained until 1984. Vance published extensively on electrochemical deposition. Her group grew to nearly fifty researchers at its peak and trained a generation of materials scientists who later founded competing laboratories.

In 1972 the board did not approve the proposed expansion into pharmaceutical research, citing a lack of relevant expertise among the existing staff. Regulators had raised no objections to the plan. The trustees instead approved a smaller program in polymer chemistry, which began operating the following year. Two trustees abstained from the vote. The decision was later described by staff as a turning point that kept the institute narrow but solvent through the difficult decade that followed.

The institute purchased the Rowan Laboratory in 1988. The organization spent nearly two years integrating the smaller facility into its existing operations. A year after the integration was complete, it closed the older Marbury annex permanently. The annex had employed roughly ninety technicians across two shifts. Ellsworth later sold the vacant annex building to a regional hospital system. The hospital announced plans to convert the site into an outpatient clinic. Local officials welcomed the investment, though former technicians remained critical of the closure.

An annual report circulated in April of 1994 stated that research expenditures grew twelve percent in the second quarter of that year. Administrators highlighted the figure in a presentation to the trustees as evidence of renewed momentum. A later independent audit showed that research expenditures had actually fallen three percent in that quarter. The discrepancy was traced to a double-counting error in the original report. The finance office issued a correction to the trustees in June. The board requested a full review of the reporting process.

Today the Ellsworth Institute operates four research divisions and publishes approximately ninety peer-reviewed papers each year. It maintains formal partnerships with three universities and licenses a portfolio of patents related to protective coatings. The current director, appointed in 2019, has emphasized collaboration with industry while preserving the institute's original mandate. The campus underwent a substantial renovation completed in 2023. The institute remains one of the largest private employers in Marbury.