Interstate 275 (I-275) in the State of Florida is a 60.7 miles (97.7 km) long highway, serving the Tampa Bay Area. Its southern terminus is at Interstate 75 near Palmetto, where I-275 heads west towards the Sunshine Skyway Bridge crossing over Tampa Bay. I-275 then passes through St. Petersburg before crossing Tampa Bay once again on the Howard Frankland Bridge, and then it enters the City of Tampa, where it has an interchange with Interstate 4 in the middle of Tampa. After this interchange, I-275 passes north through the suburbs of Tampa to its northern terminus at Interstate 75 in Wesley Chapel.

Some say[who?] that Interstate 275 and its parent route, Interstate 75, follow the opposite of the usual conventions of freeway routing. Normally, the parent route runs through a metropolitan area while an Interstate with a three-digit number (beginning with an even number) serves as the bypass route. However, in this case I-275 runs through Tampa and St. Petersburg while I-75 serves as the bypass route.

On some street maps dating around 1970 through early 1990s, I-275 from I-4 to St. Petersburg was referred to as the "Tampa Expressway". In November 2005, The Florida Legislature dedicated the section of I-275 in Pinellas County as the "St Petersburg Parkway/William C. Cramer Memorial Highway". William Cato Cramer was a native of St. Petersburg who served as a member of the Florida Legislature from 1955 through 1971. He helped to procure the building of I-275 through Pinellas County.

Just north of the Sunshine Skyway in Gulfport, drivers briefly drive on the left side as the freeway's lanes invert for about 1/2 mile (about 1 km) at the US 19/Pinellas Bayway exit (Exit 17).

Due to a failed effort during the 1970s to convert the Gandy Bridge corridor into a freeway, the Gandy Boulevard Interchange is incomplete. Two ramps were added in 1979 to eliminate illegal U-turns.

The only major interchange on I-275 is with I-4, just north of downtown Tampa. Known locally for years as "Malfunction Junction", the interchange quickly became full of daily rush hour backups due to the sprawling growth of the Tampa Bay area and the lack of the interchange's capacity. The interchange was overhauled, with wider lanes and some reconfigurations, between October 2002 and December 2006.

I-275 originally opened as a segment of I-75 in 1962 from the present northern terminus to a diamond interchange at Bearss Avenue. In the meantime, the portion of Interstate 4 that would later become a part of I-275, the Howard Frankland Bridge and its short freeway stubs at the bridge's endpoints, opened to traffic about a year earlier. In 1964, the stub of what was then known as I-4 between 50th St (through "Malfunction Junction") and Armenia Avenue was completed, with the "Malfunction Junction's" northern end was a pair of ramp stubs that would later be filled in by I-75. In 1965, the segment of I-75 from "Malfunction Junction" to about Sligh Avenue was completed. By 1967, the remaining gaps in I-4 and I-75 were filled and opened to traffic.

Around 1970, plans for the extension of I-75 into Pinellas County began. However, the first round of local opposition would lead to the eventual (and repeated) delays of I-75 through St. Petersburg. The first setback was led by 4th Street business owners and residents who demanded that construction on I-75 be stopped since the bridge was already funneling unwanted traffic onto the corridor. It has since seen many unforeseen business and residential booms, due to the building of this bridge. At the same time, construction began on I-75 from Roosevelt Boulevard to about 38th Avenue North. By this time, I-4 was truncated to "Malfunction Junction", allowing the I-75 designation take over the freeway from the junction to 4th Street North. This segment was opened to traffic in 1973, with the gap between Roosevelt and 9th Street filled in a few years later. Around this time, I-75W was resigned I-275. After some more local opposition, I-275 was constructed to meander down to 5th Avenue N, near downtown St. Petersburg, in 1975.

Probably one of the largest setbacks for I-275 was in the mid-1970s when it was proposed to go through southwest St. Petersburg towards the Sunshine Skyway Bridge. Heavy community opposition delayed this construction for several years. In the end, numerous homes and businesses were torn down and several churches were relocated. Financial burdens through this part of the project also caused further delays. However, I-375 opened partially to traffic in 1979, with full operation by 1981, and I-175 opened up in 1980.

With both downtown feeders now opened, I-275 was extended to 28th Street South. However, another round of community revolts delayed the segment of I-275 between 28th Street S and 22nd Avenue South. In spite of this, the stretch was eventually built by 1981. Exit 20 was configured for an anticipated westward expansion to a planned Pinellas Beltway. A freeway revolt killed many of Pinellas County's freeways during the 1970s, and as mentioned above, repeatedly delayed the construction of I-275. In addition, the Skyway Bridge disaster on May 9, 1980, where the freighter Summit Venture took down one of the two spans and killed 35 people, cost the bridge its Interstate Highway standards (due to only one of the two-lane spans being operable afterwards) and would not regain it until the opening of the present bridge in April 1987.

In 1982, the segment between 22nd Avenue South and 39th Avenue South was opened to traffic. As mentioned above, the Pinellas Bayway/US 19 concurrency, opened to traffic in 1983-84, is inverted for about half a mile. The reason to this configuration is unknown, however, to this day, traffic continues to flow smoothly through the interchange with very little congestion. At about the same time this interchange opened, I - 275 was complete from the Sunshine Skyway Bridge to the southern terminus with I-75 in Manatee County.

With the new Sunshine Skyway Bridge opening in 1987, the final link of I - 275, between US 19 and the bridge, was completed and opened to traffic.

The segment of I-275 between the Veterans Expressway and Himes Avenue was widened from four to six lanes in 1974. Additionally, a median barrier was built along the highway from Himes Ave to Downtown Tampa.

Until the 1980s, the Memorial Hwy/Veterans Exwy interchange was only a half diamond and the West Shore Blvd interchange was a full diamond. Both interchanges underwent drastic changes to allow safe, free-flowing movement to and from Tampa International Airport and the Veterans Expressway. Among the improvements, three free flowing exit and entry ramps were added to the expressway from I-275. The exit ramp from I-275 south to the Veterans Expressway northbound was reconstructed and the ramp from Memorial Highway northbound from Kennedy Blvd onto northbound I-275 was removed, along with the two western ramps onto West Shore Blvd (truncating the West Shore interchange to a half-diamond), in order to deter accidents that were being caused by commuters entering and exiting the interstate from the Veterans Exwy. In addition, connections from I-275 north, to Cypress St were made (though the ramps are under-utilized today). In 2004, the ramp from southbound Veterans Exwy to southbound I-275 was realigned in order to ease congestion on the mainline lanes of the interstate.

In 1984, the Himes Ave exit/entrance was constructed. The exit was originally rumored to supplement a failed redevelopment project in the area during that time. Today, the Himes Ave connection serves as reliever for nearby Raymond James Stadium.

In 1991, following the expansion of the Howard Frankland Bridge, the 4th St N interchange was reconstructed.

In 1994, the two drawbridges on the northern approach to the Sunshine Skyway Bridge, dating to the original twin Skyway bridges, were replaced with high-level fixed spans, eliminating bottlenecks caused by openings.

Between 1994 and 1998, I-275 saw very few changes, as there were no major projects taking place on the highway. The hiatus ended in 1999, when a much needed, dual-stage, widening project took place between Busch Blvd (State Road 580) and Bearss Ave. The project widened I-275 mainline from four to six lanes, rehabilitated the existing concrete surfaces, and improved interchange flow, lighting, signage, and drainage. The project wrapped up in 2003.

The northern toll plaza to the Sunshine Skyway Bridge was relocated in 2000 due to a lack of capacity, moving it south of the approach bridge. The original plaza only allowed three lanes while the replacement allows six lanes to flow through, with the sixth lane dedicated for SunPass users.

In 2001, the widening project for I-275 between Gandy Blvd and Roosevelt Blvd began. The project increased I-275 from six to eight lanes in width and its existing concrete surfaces were rehabilitated. A reconfiguration of the Roosevelt Interchange (Exit 30) started in 2001 and added access to 118th Ave N at the same interchange. The new connection to 118th Ave N is actually the first phase of a proposed freeway to connect I-275 to the Bayside Bridge (although it is unclear if future segments will be built). All construction in this area was completed by 2002. Reconstruction of I-275 between Roosevelt Blvd and 4th St N quickly followed the above widening project. Lane counts on I-275 were increased from four to mostly six lanes (with some eight lane segments). The Ulmerton Rd and 9th St N interchanges were originally narrow 1959 configurations that caused much congestion in the area.

Additionally, the 9th/MLK St N exit and Ulmerton Rd entrance ramps were situated in the left lane of I-275, causing dangerous weaving patterns. These interchanges were reconstructed into right lane configurations and two new ramps were added from Ulmerton Rd (one leading to 9th St N and one exiting onto southbound I-275. The southbound I-275 exits to Ulmerton and MLK St N were combined into one exit ramp to provide better flow. The MLK St N interchange was shut down for several months as a result of the reconstruction. Lastly, the ramps to/from 118th Ave N were opened to traffic. The entire reconstruction project along I-275 in the Gateway area wrapped up in 2005.

In 2003 Operational Improvements began for the notorious "Malfunction Junction" in downtown Tampa. The project consisted of widening mainline I-275 and I-4, along with an array of ramp/bridge improvements, lighting and drainage work, and new signs. The entire project was completed on December 22, 2006 with ITS components installed by March 2007. The renovation of the I-4 corridor through Ybor City finished around summer 2007, almost one year ahead of schedule.

The staged reconstruction project for I-275 between the Howard Frankland Bridge and Downtown Tampa was supposed to begin in the summer of 2006. Unfortunately, bids received by FDOT for the project came in at $100 million (40%) over the projected estimates. This is being blamed on by the rising cost of asphalt and other materials, which in turn is being partly blamed on the rising oil prices worldwide. As a result, FDOT has commenced with the project in four smaller phases rather than the original, large-scale, two-phase project. Construction began on phase one, the northbound lanes (south of the existing interstate) between Himes Ave and downtown Tampa, on August 13, 2007 and was completed in April 2010. Phase two, which includes construction of the northbound lanes from the WestShore area to Himes, was originally scheduled to begin in 2008, but has since been delayed further. The third phase will consist of transferring northbound traffic onto the new northbound lanes, southbound traffic onto the existing northbound lanes, and the construction of the new southbound lanes from Himes to Downtown. Finally, the fourth and final phase will construct the new southbound lanes from the WestShore area to Himes. The entire project was originally scheduled to be completed by around 2013 or 2014 (this is now likely to be delayed until 2015 or 2016) and will cost around an estimated $540 million, which is up from the original $350 million budget.

Between Himes Avenue and downtown, southbound (westbound) traffic has been shifted on to the original northbound lanes. However, those wishing to exit at either the Howard/Armenia or Himes Avenue exits do in fact continue on the original southbound lanes. Those exiting on Himes Avenue have one dedicated lane on the original southbound lanes. Traffic entering the freeway from Armenia Ave now does so on the original northbound exit ramp. This creates an odd left lane merge situation. However, to help motorists in this effort, the entrance ramp has a dedicated lane from the freeway entrance until just over the Himes Avenue bridge. Traffic heading northbound on Howard Avenue must now turn left onto Green Ave. left onto Armenia Avenue and then right on the entrance ramp in order to get on the freeway. While this setup is temporary, it has seemed to somewhat improve traffic flow in the area as motorists who intend to exit at Howard/Armenia or Himes are now off of the freeway much earlier.

In January 2011, construction began on widening the northernmost segment of I-275 from US 41 (Nebraska Ave) to the I-75 apex from four to six lanes. The project also includes constructing a dedicated flyover ramp over I-75 towards State Road 56. This ramp, along with a new, extended ramp from I-75 to SR 56, opened on August 18, 2011.

On February 4, 2011, a new ramp connecting northbound I-275 to 118th Ave N opened. This project began in July 2009 and involved widening the existing ramp from northbound I-275 to Roosevelt Blvd and is in conjunction with the project to build the Mid Pinellas Expressway, which has suffered numerous delays due to a lack of funding.

Other sections not requiring a full scale reconstruction have undergone improvements.

The segment of I-275 in Manatee County has not changed dramatically since its construction in 1983, other than a toll plaza upgrade in the late 1990s, and resurfacing of the mainline lanes between the I-75 apex and the US 19 exit. It is unclear if any other improvements are planned at this time.

Interstate 275 has two rest areas - one at each end of the Sunshine Skyway Bridge. Both rest areas, each accessible by traffic in both directions, have rest rooms, vending machines, picnic tables, dog walk areas and nighttime security. These rest areas also provide access to the fishing piers, for an extra fee.