There's no single major that can prepare you to provide humanitarian aid, and the right major is partially dependent upon what kind of work you want to do. You might have to pursue graduate education for some forms of humanitarian aid, but in other cases, you can join an organization such as the Peace Corps or gain an entry-level position at a nonprofit or non-governmental organization immediately after you graduate.
When a disaster strikes, there's often an urgent need for medical care and mental health counseling. Consider majoring in pre-medicine or psychology, then pursuing medical school or a graduate degree in psychology. If graduate school isn't for you, you might want to consider becoming a paramedic. Some schools, such as Indiana University, offer bachelor's degrees in paramedic science, and training as a paramedic can help you provide emergency aid to injured people.
You might not think about business when you consider humanitarian aid, but if you're interested in running a nonprofit organization, a degree in management could prepare you for this career. You might also be interested in pursuing training in emergency management, which will give you the skills you need to manage a staff and volunteers in the midst of a humanitarian crisis. Schools such as Adelphi University, Tufts University and Tulane University offer bachelor's degrees in emergency management.
The politics of humanitarian aid can affect decision-making, and a basic familiarity with foreign cultures can improve your effectiveness. A degree in international relations can give you a framework for understanding political disasters. If you're interested in working in a particular location, you might want to major in a field related to that culture, such as Arab studies or Spanish history.
To provide humanitarian aid, your organization will have to be properly funded. Majoring in accounting or finance can help you understand the ins and outs of managing a nonprofit, and a certification in fundraising can make you an even more valuable candidate. Degrees such as marketing can help you learn how to effectively market a nonprofit, and a degree or certification in grant writing can help you effectively lobby for grants.