OmniTRAX, Inc. is a transportation and transportation infrastructure holding company based in Denver, Colorado, in the United States. It primarily owns or operates railroads, with a network of over 30 regional and shortline railroads in 18 U.S. states and two Canadian provinces. It is one of the largest privately owned railroad companies in the United States. The firm also invests in, develops, and operates ports, multimodal transportation terminals, and industrial parks.

OmniTRAX was incorporated in 1986 as a subsidiary of The Broe Group, a privately held energy development and real estate company founded by Denver businessman Pat Broe in 1972. OmniTRAX purchased the Great Western Railway of Colorado that year in order to augment the value of Broe's industrial real estate developments in northeastern Colorado.

OmniTRAX leased the 278-mile (447 km) Kansas Southwestern Railway from the Union Pacific Railroad in April 1991.

In June 1992, OmniTRAX purchased all the outstanding stock of the Chicago West Pullman Transportation Co., which owned the 1.78-mile (2.86 km) Manufacturers' Junction Railway at Cicero, Illinois; the 13-mile (21 km) Newburgh and South Shore Railroad at Cleveland, Ohio; the 72-mile (116 km) Chicago Rail Link at Chicago, Illinois; the 25-mile (40 km) Chicago, West Pullman and Southern Railroad in Chicago; the 17.3-mile (27.8 km) Georgia Woodlands Railroad in Warren and Wilkes counties, Georgia; and the Wisconsin and Calumet Railroad in southern Wisconsin and northern Illinois. The Wisconsin & Calumet was sold less than a month later to the Wisconsin and Southern Railroad. OmniTRAX purchased the abandoned Western Electric Hawthorne Works in Cicero, which was adjacent to the Manufacturers' Junction Railway, and began developing it as a multimodal transfer center.

In October 1992, OmniTRAX purchased 800 miles (1,300 km) of track in Kansas and Oklahoma from the Atchison, Topeka & Santa Fe Railway. The main lines of track stretched from Salina, Kansas, to Osborne, Kansas, and from Marion, Kansas, to Scott City, Kansas. OmniTRAX formed the Central Kansas Railway to run on the lines. The Kansas Southwestern Railway merged into the Central Kansas Railway in May 2000, and then OmniTRAX sold the Central Kansas Railway to Watco in April 2001.

OmniTRAX purchased 31 miles (50 km) of track between Borger and Panhandle, Texas, from the Atchison, Topeka & Santa Fe in November 1993. It formed the Panhandle Northern Railroad to operate on this track. Eighteen months later, in May 1995, OmniTRAX leased the 25.5-mile (41.0 km) Northern Ohio & Western Railway from the Sandusky County/Seneca County/Tiffin Port Authority.

OmniTRAX moved into Canada in November 1996 with its purchase of the Hudson Bay Railway, which ran from The Pas, Manitoba, to the Port of Churchill in Churchill, Manitoba. OmniTRAX then purchased the port itself for C$1 in November 1997. As part of the deal, the Canadian government agreed to put C$34 million worth of upgrades, dredging, and repairs into the port, while OmniTRAX pledged to add C$45 million in upgrading the port facilities and Hudson Bay Railway. Three months later, OmniTRAX purchased the Carlton Trail Railway track bought from the Canadian National Railway. The 280 miles (450 km) ran from Warman, Saskatchewan, to White Star, Saskatchewan, and from Speers Junction (near White Star) to end of the line at Meadow Lake, Saskatchewan.

OmniTRAX expanded its presence in the American Southeast in 2004 by purchasing the 245-mile (394 km) Georgia and Florida Railnet (renamed the Georgia and Florida Railway) from North American RailNet. It also leased the 22-mile (35 km) terminal switching Fulton County Railway (based in Atlanta), and the Alabama and Tennessee River Railway in Alabama. It purchased both lines outright in 2018.