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Human Resources Business Partner

Torrance, California, United States
Full Time On-site

The Human Resources Business Partner (HRBP) serves as a strategic advisor to leaders and employees, helping drive organizational effectiveness, talent development, and workforce performance across Castelion. This role partners closely with business leaders to align people strategies with company objectives, providing guidance on organizational design, performance management, employee relations, leadership development, and workforce planning. The ideal candidate thrives in a fast-paced, high-growth environment and is passionate about building scalable people practices that enable exceptional talent to perform at their highest level while supporting Castelion's mission and continued growth.

Responsibilities

Strategic Business Partnership

  • Partner with business leaders to improve organizational performance, workforce planning, and team effectiveness, maintaining a 95%+ leadership satisfaction rating through proactive HR support.
  • Provide strategic coaching that enables leaders to resolve 90%+ of employee relations and performance matters without escalation.
  • Develop and execute people strategies that improve retention, organizational health, and business outcomes, contributing to year-over-year improvements in key talent metrics.

Organizational Effectiveness & Talent Strategy

  • Lead workforce planning, talent reviews, and organizational design initiatives that ensure 100% of critical roles have succession or staffing plans.
  • Partner with leaders to identify and develop high-potential talent, achieving 90%+ completion of annual talent calibration and development plans.

Performance Management & Employee Relations

  • Coach leaders through performance management, investigations, and employee relations matters while maintaining 100% legal and policy compliance.
  • Ensure 95%+ of performance improvement plans, corrective actions, and investigations are completed within established timelines and documentation standards.

Leadership Coaching & Development

  • Coach managers to improve leadership capability, accountability, communication, and decision-making, resulting in measurable improvements in team performance.
  • Partner with leaders to increase manager effectiveness, with 90%+ of leaders demonstrating improvement against leadership development objectives.

Culture & Operational Excellence

  • Identify and implement process improvements that reduce administrative effort and improve service delivery, targeting 20%+ annual efficiency gains across HR processes.
  • Drive People initiatives that reinforce Castelion's culture of ownership, accountability, urgency, and continuous improvement while maintaining 95%+ completion of key annual People programs.

Basic Qualifications

  • 5+ years of progressive HR experience, including HR Business Partner experience supporting technical, engineering, manufacturing, and/or operations organizations.
  • Demonstrated experience supporting both exempt and non-exempt employee populations in a fast-paced environment.
  • Experience supporting workforce planning, talent development, organizational design, and performance management initiatives.
  • Strong understanding of employment law, employee relations, and HR best practices.
  • Demonstrated ability to influence without authority and build credibility across all levels of an organization.
  • Comfortable operating in a fast-paced, highly ambiguous, high-growth environment.
  • Strong analytical skills and ability to translate people data into business recommendations.

Preferred Skills and Experience

  • Experience supporting aerospace, defense, manufacturing, hardware, or other highly technical organizations.
  • Experience supporting organizations undergoing hypergrowth.
  • Master's degree, PHR, SPHR, SHRM-CP, or SHRM-SCP certification.

Other Duties

Please note this job description is not designed to cover or contain a comprehensive listing of activities, duties or responsibilities that are required of the employee for this job. Duties, responsibilities and activities may change at any time with or without notice.

Benefits And Perks

All full-time employees are granted meaningful long-term equity, sharing in the company's significant growth trajectory. We offer four (4) weeks of paid time off, ten (10) company-paid holidays, and comprehensive health benefits - including 100% employee-covered medical and strong dependent coverage, along with dental and vision plans. We also provide paid parental leave to support growing families, a $100 monthly fitness stipend to promote health and performance, and onsite EV charging for convenience. In addition, employees enjoy perks like catered meals, company-covered food during high-demand periods, and a fully stocked kitchen to stay fueled throughout the day.

While this position does not currently require a U.S government-issued security clearance, it may in the near future. Therefore, the ability to obtain and maintain a U.S. government–issued security clearance is required. U.S. citizenship is required, as only U.S. citizens are eligible for a security clearance.

Affirmative Action/EEO Statement

About Castelion

Castelion

Castelion is one of the fastest-rising defense technology companies focused on building affordable, rapidly deployable hypersonic strike systems for the U.S. military. Founded by former SpaceX leaders, the company is working to modernize how advanced weapons are developed and manufactured—using rapid iteration, vertical integration, and scalable production to deliver next-generation deterrence capabilities faster than traditional defense programs. Castelion’s mission centers on restoring America’s ability to field advanced military technology at speed and scale.

For job seekers, Castelion offers the opportunity to work directly on some of the most advanced technologies in national defense, including propulsion systems, avionics, flight software, guidance and navigation, missile systems, and advanced manufacturing. The company hires across aerospace engineering, embedded software, manufacturing, test engineering, avionics, cybersecurity, and operations—making it especially attractive to engineers, builders, veterans, and mission-driven professionals who want hands-on ownership of real hardware.

Unlike traditional defense contractors, Castelion operates with a startup-style engineering culture modeled after rapid aerospace development environments. Employees work closely with flight hardware, testing, and production systems in a fast-paced setting where speed, accountability, and execution are prioritized. The company openly emphasizes a builder mentality—giving team members the chance to own major projects and contribute directly to systems with national security impact.

As the U.S. military increases investment in hypersonic weapons, missile modernization, and scalable deterrence capabilities, Castelion continues to grow rapidly through major government contracts and manufacturing expansion. For professionals seeking a high-growth aerospace and defense company where they can help shape the future of national security technology, Castelion is quickly becoming one of the most exciting employers in the defense innovation ecosystem.

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