Human Resources Business Partner Torrance, CA Human Resources

Castelion is moving incredibly fast to develop and deliver advanced defense systems at a time when execution matters more than ever. We believe focus, ownership, and excellence are decisive advantages - and we're building a world-class team to turn bold ideas into real capability.

This is a rare opportunity to join at an early stage, where you'll have significant ownership, collaborate with exceptional teammates, and make a direct, measurable impact on our mission and the future of the company - regardless of your function.

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.

• 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.

• 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.

• 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.

• 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.

• 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.

• 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.

• 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.

Castelion offers a generous benefits package. Please refer to the bottom of our Careers page for more details.

Please note this job description is not designed to cover or contain a comprehensive listing of activities, duties or…