211info provides information and resources for various needs including health care, housing, and crisis hotlines.

The Northwest Sarcoma Foundation provides support, education, and advocacy for individuals affected by Sarcoma, while funding research to improve treatment options.

This organization provides information and support for patients and their families regarding rights, options, and services available at the hospital.

NTM Info & Research supports individuals affected by nontuberculous mycobacterial (NTM) lung disease and bronchiectasis, providing education, advocacy, and resources for patients and healthcare providers.

The Bijniervereniging supports individuals with adrenal disorders, providing information and advocacy services to connect patients and address their needs.

This organization focuses on women's health issues, providing information and resources related to various conditions such as menopause, pregnancy, and reproductive health.

OMF is the leading resource for eye cancer research funding, education, and patient/caregiver support, focusing on ocular melanoma.

The Office of Minority Health works to improve the health of racial and ethnic minority populations and American Indians and Alaska Natives, focusing on eliminating health disparities.

The OMSLife Foundation raises awareness of Opsoclonus Myoclonus Syndrome, maintains a support network for caregivers, and funds research for a cure.

The Oral Cancer Foundation is dedicated to reducing suffering and saving lives through prevention, education, research funding, advocacy, and patient support activities for oral and oropharyngeal cancers.

ORD India is a national umbrella organization advocating for the rights and resources of people with rare diseases in India, focusing on public awareness, policy development, and access to treatment.

O.U.C.H (Organization for the Understanding of Cluster Headaches) was a non-profit organization dedicated to advocating for and supporting individuals affected by cluster headaches, but it is no longer active.

Orphanet is a resource dedicated to improving knowledge on rare diseases to enhance diagnosis, care, and treatment for patients, while providing high-quality information and ensuring equal access for all stakeholders.

The OI Foundation is the only voluntary national health organization dedicated to helping people cope with OI.

Ostomy Canada Society provides support, education, and resources for Canadians living with an ostomy, helping them to live life to the fullest.

This organization provides information and support for individuals affected by Primary Orthostatic Tremor (OT), a rare neurological movement disorder characterized by high frequency tremors in the legs when standing.