The Brodie helmet (also called the shrapnel helmet or Tommy helmet, and in the United States known as a doughboy helmet) was a steel helmet designed and patented in 1915 by John L. Brodie.

During the first year of World War I, none of the combatants offered steel helmets to their troops. The soldiers of most nations went into battle wearing simple cloth caps that offered virtually no protection from modern weapons. German troops were wearing the traditional leather Pickelhaube, with a covering of cloth to protect the leather.

The huge number of lethal head wounds that modern weapons were inflicting upon the French Army led them to introduce the first steel helmets in the summer of 1915. The first of these helmets were steel "skullcaps" worn under the cap, inspired by the tale of a soldier who survived a potentially lethal wound by wearing a bowl on his head. However it was soon replaced by the Adrian helmet (designed by August-Louse Adrian). It began to replace the traditional French kepi and was later adopted by the Belgian and Italian armies. At about the same time the British War Office had also seen a similar need for steel helmets.

The helmet had a shallow circular crown with a wide brim around the edge, a leather liner and a leather chinstrap. The helmet's "soup bowl" shape was originally designed to protect the wearer's head and shoulders from shrapnel falling from above. The shallow bowl design allowed the use of relatively thick steel that could be formed in a single pressing while maintaining the helmet's thickness. Although this made it more resistant to projectiles, the design offered less protection to the lower part of the head and neck than other designs. The steel helmet was known to the troops as a "tin hat" or for the officers a "battle bowler" and, with typical black humour, a bayonet was sometimes called a "tin opener".

The original design (Type A) was made of mild steel with a brim 1.5 - 2 inches wide. The Type A was in production for just a few weeks before the specification was changed and the Type B was introduced. The Type B was made of hardened manganese steel, had a narrower brim and had a more domed crown. In May 1916 the Mark I began to be issued. The Mark I had a matt finish textured with sawdust or crushed cork to prevent reflection. The Mark I was issued in large numbers and saw out the rest of the War. In 1917 the liner was modified to include a rubber cushion to make it more comfortable (this was not adopted for the M1917). Helmets were often painted with unit insignia towards the end of the war, and are often called "parade helmets" by collectors.

The basic Brodie patterned helmet was used by the US Army until 1942 with minor modifications including a totally new liner, and canvas chinstrap. This basic design was used well into World War II, until finally completely superseded by the M1 Helmet in 1942. The Brodie pattern continued to be used (as the slightly modified Mark II) by the British and Commonwealth forces throughout World War II. During this period the helmet was also used by the Police, the Fire brigade and ARP wardens in Britain. There was also a 'civil' pattern available which was a little deeper but made from ordinary mild steel, and which was available for private purchase.

In 1944, the British replaced it with a significantly modified design known as the British Pattern 1944, 'Turtle' or, occasionally, the Mark III. This was a deeper helmet with a smaller brim and provided better protection, particularly at the sides.

In the late 1980s the British replaced steel helmets with kevlar ones.