The RIM-174 Standard Extended Range Active Missile (ERAM), or Standard Missile 6 (SM-6), is a missile in current production for the United States Navy (USN). It was designed for extended-range anti-air warfare (ER-AAW) purposes, providing capability against fixed and rotary-wing aircraft, unmanned aerial vehicles, anti-ship cruise missiles in flight, both over sea and land, and terminal ballistic missile defense. It can also be used as a high-speed anti-ship missile. The missile uses the airframe of the earlier SM-2ER Block IV (RIM-156A) missile, adding the active radar homing seeker from the AIM-120C AMRAAM in place of the semi‑active seeker of the previous design. This will improve the capability of the Standard missile against highly agile targets and targets beyond the effective range of the launching vessels' target illumination radars. Initial operating capability was planned for 2013 and was achieved on 27 November 2013. The SM-6 is not meant to replace the SM-2 series of missiles but will serve alongside and provide extended range and increased firepower. It was approved for export in January 2017. An air-to-air variant of the SM-6, known as the AIM-174 Gunslinger, is the first dedicated long-range air-to-air missile employed by the USN since the 2004 retirement of the AIM-54 Phoenix. The SM-6 can also be fired from the U.S. Army's Typhon missile launcher as part of the Strategic Mid-range Fires System (SMRF).

The Standard ERAM is a two-stage missile with a booster stage and a second stage. It is similar in appearance to the RIM-156A Standard missile. The radar seeker is an enlarged version adapted from the AIM-120C AMRAAM seeker (13.5 in (34 cm) versus 7 in (18 cm)). The missile may be employed in a number of modes: inertially guided to target with terminal acquisition using active radar seeker, semi‑active radar homing all the way, or an over-the-horizon shot with Cooperative Engagement Capability (CEC). The missile is also capable of terminal ballistic missile defense as a supplement to the Standard Missile 3 (RIM-161).

The SM-6 offers extended range over previous SM-2 series missiles, primarily being able to intercept very high altitude or sea-skimming anti-ship missiles, and is also capable of performing terminal phase ballistic missile defense. The SM-6 can also function as a high-speed anti-ship missile. It can discriminate targets using its dual-mode seeker, with the semi‑active seeker relying on a ship-based illuminator to highlight the target and the active seeker having the missile itself send out an electromagnetic signal; the active seeker has the ability to detect a land-based cruise missile amid ground features, even from behind a mountain. The multi-mission SM-6 is engineered with the aerodynamics of an SM-2, the propulsion booster stack of the SM-3, and the front-end configuration of the AIM-120 AMRAAM. Estimates of the SM-6's range vary; its official published range is 130 nmi (150 mi; 240 km), but it could be anywhere from 200 nmi (230 mi; 370 km) to as much as 250 nmi (290 mi; 460 km).

The U.S. Navy is adding GPS guidance to the SM-6 Block IA so that it has the capability to strike surface targets if needed. However, given its higher cost than other land attack weapons like the Tomahawk cruise missile, it would not likely be used as a primary option. In February 2016, Secretary of Defense Ashton Carter confirmed that the SM-6 would be modified to act as an anti-ship weapon.

The SM-6 Block IB is currently in final stage development, with production expected to begin in late fiscal year 2024. The variant is to improve on the existing capabilities of the SM-6 series by incorporating a larger 53 cm (21-inch) diameter motor for greater range and speed. The Block IB variant is intended to achieve hypersonic speeds, making it highly effective against both aerial and surface targets.

The second increment of the SM-6 Sea Based Terminal is a modification to Raytheon’s missile quickly fielded to provide defense against hypersonic weapons in their terminal flight phase. It will serve as an interim solution until the Glide Phase Interceptor becomes available.

Raytheon entered a contract in 2004 to develop the missile for the United States Navy after the cancellation of the Standard Missile 2 extended range block IVA (RIM-156B). Development started in 2005, followed by testing in 2007. The missile was officially designated RIM-174A in February 2008. Initial low rate production was authorized in 2009. Raytheon received a $93 million contract to begin production of the RIM-174A in September 2009. The first low-rate production missile was delivered in March 2011. SM-6 was approved for full-rate production in May 2013. On 27 November 2013, the Standard ERAM achieved Initial Operating Capability (IOC) when it was fielded on board USS Kidd.

During exercises from 18–20 June 2014, the Arleigh Burke-class destroyer USS John Paul Jones fired four SM-6s. One part of the exercise, designated NIFC-CA AS-02A, resulted in the then-longest surface-to-air engagement in naval history; the exact range of the intercept was not publicly released. On 14 August 2014, an SM-6 was test fired against a subsonic, low-altitude cruise missile target and successfully intercepted it over land. A key element of the test was to assess its ability to discern a slow-moving target among ground clutter. On 24 October 2014, Raytheon announced that two SM-6s intercepted anti-ship and cruise missile targets during "engage on remote" scenarios. A low-altitude, short-range supersonic GQM-163A and a low-altitude, medium-range subsonic BQM-74E were shot down by SM-6s fired from a guided-missile cruiser using targeting information provided by a guided-missile destroyer. Advanced warning and cueing from other ships allows the missile's over-the-horizon capability to be used to a greater extent, allowing a single ship to defend a much larger area. In May 2015, the SM-6 was moved from low-rate to full-rate production, significantly increasing production numbers and further reducing unit cost.