Funding Amount

Up to US $25,000

Deadline

Rolling / Open

Grant Type

foundation

Deadline history & next window

Cycle
Rolling — applications accepted year-round
Tracked since
April 2026

From the program guidelines: “NOTE: Online Inquiry Forms will be reviewed by foundation staff on a rolling basis, so they may be submitted at any time during the year.”

Can we apply?

Check your organization against each line. Taken from the listing; confirm with the funder's guidelines.

Eligible organizations

  • Nonprofit organizations serving Hawaii with Internal Revenue Code Sections 501(c)(3) and 509(a) public charity status
  • Public schools

Geography

  • Based in the region or with a record of longstanding ties to the region and effective current or potential relationship

Required status

  • 501(c)(3) tax-exempt status

Not eligible / not funded

  • Not eligible: Ongoing programs
  • Not eligible: Operations
  • Not eligible: Events
  • Not eligible: Computers
  • Not eligible: Endowments
  • Not eligible: Other items as listed below
  • Not eligible: Proposals are not considered for:Individuals or businesses.
  • Not eligible: Ongoing operating expenses (except for those few organizations the Foundation deems critical to the success of its overall strategies.
  • Not eligible: The Foundation may also support a new project or organization needing start-up funding)VehiclesComputersEndowments.
  • Not eligible: Annual fund drivesSponsorships, special events, dinners, galas.
  • Not eligible: Organizations based outside of Hawaii.
  • Not eligible: Projects taking place outside Hawaii that do not benefit Hawaii

Overview

Strengthening Windward O‘ahu Communities Grant

Status: ACTIVE
Funder: Harold K. L. Castle Foundation
Amount: Up to US $25,000
Last Updated: November 21, 2025

Summary

The Harold K.L. Castle Foundation is dedicated to strengthening Windward O‘ahu communities by investing in their rich cultural heritage, youth, and natural resources. The foundation aims to enhance educational outcomes for local youth, ensuring they graduate high school with essential skills and support their future success in STEM fields. By fostering collaboration and innovation among organizations, the foundation seeks to build sustainable capacity within the region, ultimately contributing to the vitality and resilience of its communities.

Overview

NOTE: Online Inquiry Forms will be reviewed by foundation staff on a rolling basis, so they may be submitted at any time during the year. Within one month of receipt of your Online Inquiry Form, we will contact you to request more information, invite you to submit a full proposal, or inform you that the foundation will be unable to consider a full proposal due to limited resources and/or a mismatch with foundation priorities. If you are invited to submit a full proposal, it will be due at the deadlines above. Strengthening Windward O‘ahu Communities Windward Oahu Strategy: Building social, human, and natural capital with a particular emphasis towards nurturing future community leaders. The Harold K.L. Castle Foundation builds on the strengths of vibrant Windward Oahu communities through investments that support the region’s rich cultural legacy, its youth and families, and its natural resources. Like many Hawaii-based organizations, the Foundation is rooted in a strong sense of community and place. Prior to creating a family foundation in 1962, Harold K.L. Castle gave generously of his time, energy, and financial resources to the Windward Oahu community in which he lived and worked. With an eye toward the future and a vision of building civic and cultural resources, Mr. Castle in his lifetime made substantial gifts of land for Windward churches and schools, and for institutions such as Castle Medical Center and the Windward YMCA. Over its 44-year history, the Foundation has maintained a deep connection to its roots in Windward Oahu and a commitment to contributing to the vitality of communities from Kahuku to Waimanalo. Our Purpose The Harold K.L. Castle Foundation helps communities build assets in Windward Oʻahu by strengthening and supporting the region’s rich cultural legacy, its youth and families, and its natural resources. Investing in the unique history, traditions, people, and environment of Windward Oʻahu has important implications for the state as a whole, and is an important piece of the Foundation’s commitment to “Building Resources for Hawaiʻi’s Future.” Our Goals By 2027, to dramatically increase the number of Windward Oʻahu youth who complete college and attain employment success, particularly in STEM careers; By 2027, to ensure that all Windward Oʻahu students graduate high school with a mālama ‘āina mindset and the resiliency and civic skills needed to protect and restore the watersheds and fisheries of Koʻolauloa and Koʻolaupoko; and To support other unique opportunities to strengthen the health, safety, and vibrancy of the region’s communities. Our Strategy In 2017, Directors embarked on a 10 year journey to achieve three primary goals within Windward Oʻahu through four key strategies: Our Priorities Our approach to grant making over the past years has been consistent. We continue to look for organizations that can significantly leverage our grants with other sources of support, where our funds can play a catalytic role, where we can see the promise of significant impact on important public issues in Hawaii, and where there is strong leadership that can make the best use of the Harold K.L. Castle Foundation’s funds. In Windward O‘ahu, this means start-up for promising new organizations, innovation, and scaling good work when strategies align. It is with these values in mind that we lift up the following priorities for funding in Windward Oʻahu: High quality organizations and/or programs based in the region or with a record of longstanding ties to the region and effective current or potential relationships with schools and/or communityOR high performing potential partners from outside of the region that are uniquely qualified to address Foundation goal(s) within the regionHighly collaborative organizations that exhibit authentic, reciprocal relationships with schools and communitiesInnovation, capacity building, and occasionally scaling of programs that align to the strategy – the Foundation does not support ongoing programs or operationsSmall preschool improvements are welcome throughout the year, but are restricted to $25,000 or less. Larger capital requests for Windward Oʻahu are considered once per year in the fall with inquiries for such requests due October 1. Much of this work will focus on building capacity within existing people, places, and programs of the region – thereby amplifying the bright spots, accelerating progress, and realizing potential within Windward Oʻahu. This will primarily be accomplished by supporting networks, systems, and cohorts for deeper learning and impact. The intention is to ground this work deeply in community for lasting and sustainable change.

Eligibility

You can learn more about this opportunity by visiting the funder's website. Eligible applicants:Nonprofit organizations serving Hawaii with Internal Revenue Code Sections 501(c)(3) and 509(a) public charity statusPublic schools

Ineligibility

The Foundation does not fund events, computers, endowments, and other items as listed below.Proposals are not considered for:Individuals or businessesOngoing operating expenses (except for those few organizations the Foundation deems critical to the success of its overall strategies. The Foundation may also support a new project or organization needing start-up funding)VehiclesComputersEndowmentsAnnual fund drivesSponsorships, special events, dinners, galasOrganizations based outside of HawaiiProjects taking place outside Hawaii that do not benefit Hawaii

What Harold KL Castle Foundation actually gave

Source: IRS Form 990-PF, 2024

Grants in 2024
106
Total given
$6.89M
Median grant
$25K
Range
$500–$550K
  • By dollars: Hawaii 83%, California 14%, District of Columbia 4%. Top recipient cities: Honolulu, HI; Kaneohe, HI; Kailua, HI.
  • 2% of grants with a stated purpose were for general or operating support.
  • 36% of recipients were new grantees, not repeat recipients.

Example grants

  • Social Finance Inc · Boston, CA

    Proposal to serve as hawaii renewable learning fund manager [6086; pc]

    $550K

  • University of Hawaii Foundation · Honolulu, HI

    Soar higher - support for windward oahu schools to participate as a gear up 6-16 model…

    $529K

  • Hawaii Community Foundation (HCF) · Honolulu, HI

    Support for a second round of contributions to the holomua pooled fund whose goal is…

    $500K

  • Kuaaina Ulu Auamo (Kua) · Kaneohe, HI

    To support and strengthen this critically important backbone organization and its…

    $500K

  • The Nature Conservancy of Hawaii · Honolulu, HI

    Advancing community-based marine management to reach 30x30 goals [5660; pc]

    $280K

IRS Form 990-PF, 2024. Amounts as reported by the funder. Full 990 history →

Focus Areas & Funding Uses

Fields of Work

nonprofitseducationstem-educationyouth-programsfoundation

Categories

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