United States militarism refers to the reliance of the United States on its military force to pursue foreign policy goals that can be achieved more effectively by other means.

Militarism has been defined as the tendency to regard military efficiency as the supreme ideal of the state, overshadowing all other interests. In a militarized society, military institutions, the military–industrial complex and military ways of life are ranked above the ways of civilian life, and military mentality is carried over into the civilian sphere." Since the end of the Cold War, the US military has continued to grow even without any existential threat to the US, as it currently spends more than 40% of all military expenditures worldwide and has military forces stationed in more than 150 countries.

The ongoing War on Terror and the invasions of Iraq and Afghanistan have all contributed significantly to the current prominent role of the United States Department of Defense in American politics. Administrations of George W. Bush and Barack Obama have also ensured that military leaders dominate positions related to national security, to the detriment of diplomatic solutions with Iran, North Korea, or the Middle East. The recent administrations, as early as President Bill Clinton, have thus placed the Department of Defense in a position of unprecedented power and influence.

Throughout the first two centuries of American history, a potent military force was necessary to face immediate threats at the time. When these threats were lifted, the military establishment was reduced in size by policymakers. That is, the army assembled for each crisis vanished as soon as that crisis ended. This was the case in 1865, 1918, and 1945, corresponding to the Civil War, and the First and Second World Wars, respectively. For instance, the million-men-strong Union Army of 1865 dwindled to just 57,000 in a year and to less than 30,000 in another five years. This pattern continued even after the Second World War when the United States had taken on the responsibilities of a superpower. The US Army had more than eight million officers and soldiers on V-J Day in 1945. Only 1.8 million people were still on active duty after a year, and that number was cut in half again the next year.

With the start of the Cold War in 1947 and after the enactment of the National Security Act in the same year, the US military forces were automatically included in the national security doctrine during peacetime. Over the following four decades, military influence increased, leading to the 1986 Defense Reorganization Act, also known as the Goldwater-Nichols Act, which designated the chairman of the Joint Chiefs of Staff as the "principal military adviser to the President, the National Security Council, and the Secretary of Defense." Civilian academics and business researchers, including Henry Kissinger and Herman Kahn, came to prominence during the Cold War and significantly promoted the use of force. The complexity of the nuclear policy may have contributed to the rise of these "defense intellectuals" and their think tanks.

After the end of the Cold War, the United States took advantage of the collapse of the Soviet Union and the Warsaw Pact by encouraging the newly liberated nations to join the NATO, the political and military alliance of the West. Since then, it has been a policy of the US to maintain military superiority over potential adversaries. This era is marked by an increased propensity to employ force, which might have normalized war. During the Cold War era, from 1945 to 1988, there were six significant US military operations abroad. In comparison, since the fall of the Berlin Wall in 1989, nine significant military interventions have taken place, from the 1989 Operation Just Cause (the ouster of Manuel Noriega) to the 2003 Operation Iraqi Freedom (the overthrow of Saddam Hussein). In this latter period, the convergence of CIA and JSOC operators was "so complete that US officials ranging from congressional staffers to high-ranking CIA officers said they often [found] it difficult to distinguish agency [CIA] from military personnel."

Since the end of the Vietnam War in 1975, some have contended that the United States has evolved into a neo-militaristic state, characterized by its reliance on a relatively limited number of volunteer combatants, substantial reliance on sophisticated technologies, and rationalization and extension of government recruitment and advertising campaigns. The American response to the 9/11 attacks as a "global" war on terror promoted the recent remilitarization of the Western countries, and introduced the Middle East as the source of threats to the rest of the world, which helped justify the bigger efforts after 9/11 to forcefully reshape the region.

According to the prevailing national security consensus, major politicians today assume that American military dominance is an unquestionable virtue and proof of greater American superiority. They believe that this armed might holds the key to establishing a world order that supports American values. One outcome of this consensus over the past 25 years has been the militarization of US policies and the promotion of tendencies that suggest American culture as a whole is becoming more and more enamored with its self-image as the unrivaled military power. There are many distinct ways in which this new American militarism shows itself. It does so, first and foremost, in terms of the size, expense, and organizational structure of America's current military system.